- Email: [email protected]
Peripheral Nerve Sheath Tumor in the Pelvic Limb of a Domestic Rabbit (Oryctolagus cuniculus)
Accepted Manuscript
Peripheral Nerve Sheath Tumor in the Pelvic Limb of a Domestic Rabbit (Oryctolagus cuniculus) Lauren Reimnitz DVM , David Sanchez-Migallon Guzman LV, MS, DECZM (Avian, Small Mammal), DACZM , Elise LaDouceur DVM, DACVP , Sarah Stevens DVM, MS , Noemie Summa Dr Med Vet, IPSAV (Zoological Medicine) , ´ Sara Gardhouse DVM , Amir Kol DVM, AVCP, PhD , Kelsey Brust DVM , Michelle G. Hawkins VMD, DABVP (Avian) PII: DOI: Reference:
S1557-5063(17)30292-6 https://doi.org/10.1053/j.jepm.2018.04.018 JEPM 50122
To appear in:
Journal of Exotic Pet Medicine
Received date: Revised date: Accepted date:
20 October 2017 31 December 2017 3 April 2018
Please cite this article as: Lauren Reimnitz DVM , David Sanchez-Migallon Guzman LV, MS, DECZM (Avian, Small Elise LaDouceur DVM, DACVP , Sarah Stevens DVM, MS , Noemie Summa Dr Med Vet, IPSAV (Zoological Medi ´ Sara Gardhouse DVM , Amir Kol DVM, AVCP, PhD , Kelsey Brust DVM , Michelle G. Hawkins VMD, DABVP (Avian) , Peripheral Nerve Sheath Tumor in the Pelvic Limb of a Domestic Rabbit (Oryctolagus cuniculus), Journal of Exotic Pet Medicine (2018), doi: https://doi.org/10.1053/j.jepm.2018.04.018
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Peripheral Nerve Sheath Tumor in the Pelvic Limb of a Domestic Rabbit (Oryctolagus cuniculus)
Lauren Reimnitz, DVM; David Sanchez-Migallon Guzman, LV, MS, DECZM (Avian, Small
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Mammal), DACZM; Elise LaDouceur, DVM, DACVP; Sarah Stevens, DVM, MS; Noémie Summa, Dr Med Vet, IPSAV (Zoological Medicine); Sara Gardhouse, DVM; Amir Kol, DVM, AVCP, PhD; Kelsey Brust, DVM; Michelle G. Hawkins, VMD, DABVP (Avian)
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From the Department of Medicine and Epidemiology (Sanchez-Migallon Guzman, Hawkins), William R. Pritchard Veterinary Medical Teaching Hospital (Summa, Gardhouse), Department of Pathology, Microbiology, and Immunology (LaDouceur, Stevens, Kol), and Department of
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Surgical and Radiological Sciences (Brust), School of Veterinary Medicine, University of
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California, Davis, One Shields Avenue, Davis, CA 95616
Corresponding author: David Sanchez-Migallon Guzman
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Department of Medicine and Epidemiology, School of Veterinary Medicine, University of
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California at Davis, One Shields Ave, 2108 Tupper Hall, Davis, CA 95616. Email: [email protected]
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Phone: (530) 752-1393 Fax: (530) 752-8906
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Peripheral Nerve Sheath Tumor in the Pelvic Limb of a Domestic Rabbit (Oryctolagus
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cuniculus)
Abstract
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A 3-year-old, 4.0 kg, female, spayed Silver Marten cross rabbit (Oryctolagus cuniculus) was presented for evaluation of a suspected recurring spindle cell sarcoma following primary excision by the referring veterinarian. Physical examination revealed a large subcutaneous mass on the left metatarsus and a fine needle aspirate revealed suspected neoplastic spindle cells.
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Hematologic evaluation was unremarkable and a computed tomography scan revealed invasion
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of the mass into skeletal muscles but showed no evidence of metastatic disease. An amputation was performed, after which the patient recovered uneventfully. However, the rabbit was found
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suddenly dead at time of discharge from unknown cause. Gross, histologic, and
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immunohistochemical evaluation was performed, which diagnosed a peripheral nerve sheath tumor. To the authors’ knowledge, this is the first detailed case report of a lagomorph
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peripheral nerve sheath tumor specifically confirmed with immunohistochemistry. Wide surgical excision is considered the treatment of choice and may be combined with radiation therapy. Further research is required to determine risk factors, the role of adjunctive therapy, as well as long term prognoses for peripheral nerve sheath tumors in rabbits. Key words
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Spindle cell sarcoma; lagomorph; amputation; metatarsus; neoplasia
Case description
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A 3-year-old, 4.0 kg, female, spayed Silver Marten cross rabbit (Oryctolagus cuniculus) was presented to the University of California Veterinary Medical Teaching Hospital (UCD; Davis, CA, USA) as a referral for a suspected recurring spindle cell sarcoma on her left pelvic limb.
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Previous history included pododermatitis, a right-sided head tilt, and a repaired abdominal hernia. A 3 x 6 cm, soft, fluctuant mass was noted on the medial aspect of her left metatarsus three and a half weeks prior to presentation at UCD. Mass removal was performed by the referring veterinarian one week later, at which time it was noted that the ventral aspect of the
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mass was infiltrating between metatarsal bones. The rabbit was discharged on enrofloxacin (10
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mg/kg orally every 12 hours; Bayer Healthcare, Shawnee Mission, KS, USA), and meloxicam (0.2 mg/kg orally every 12 hours; Metacam; Boehringer Ingelheim, Vetmedica, St. Joseph, MO, USA)
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and silver sulfadiazine cream (Ascend Laboratories, Montvale, NJ, USA) applied to the surgical
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site with daily bandage replacement. Histopathology revealed an incompletely excised spindle cell sarcoma.
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On presentation to UCD, physical examination findings revealed a fluctuant, 3 x 6 cm, subcutaneous mass deep to the previous surgical site. The remainder of the physical exam revealed a slight right-sided head tilt and grade I-II/VI pododermatitis on all limbs. A fine needle aspirate was performed and revealed suspected neoplastic spindle cells (Fig. 1). The client was
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advised to discontinue bandage changes and the current medications and a computed tomography (CT) scan was scheduled. On return examination three weeks later, the mass had increased in size to 9 x 5 x 3.5 cm with a 5 x 5 cm central ulcer. A complete blood count and chemistry panel were performed
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and were unremarkable. The next day, the rabbit was anesthetized for a whole-body CT scan with contrast. The CT scan revealed extension of the mass from the caudal left stifle to the medial aspect of the distal left metatarsus (~16 cm in length) (Fig. 2). Proximally, the mass
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invaded skeletal muscles without evidence of bone invasion/reaction. The left popliteal lymph node was enlarged to 1 x 0.5 cm. Imaging of the thorax and abdomen were unremarkable without evidence of metastatic disease. A limb amputation was scheduled for 8 days later. On return to UCD one day prior to surgery, the mass was multifocally necrotic, and the
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remainder of the physical examination was static. Bandages were changed daily in the hospital.
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Meloxicam and tramadol treatments continued, and the antibiotic was changed to chloramphenicol (50 mg/kg by mouth every 12 hours; Bimeda Inc., Le Sueur, MN).
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The following day the rabbit underwent a left coxofemoral amputation. Premedication
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was achieved with oxymorphone (0.2 mg/kg intramuscularly; Opana, Endo Pharmaceuticals Inc., Chadds Ford, PA, USA), midazolam (1 mg/kg intramuscularly), and glycopyrrolate (0.01
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mg/kg subcutaneously; West-Ward, Eatontown, NJ, USA). An IV catheter was placed and the rabbit was induced with ketamine (1.5 mg/kg intravenously; KetaVed, VedCo, St. Joseph, MO, USA) and midazolam (0.58 mg/kg intravenously), and oxymorphone (0.1 mg/kg intramuscularly). Intravenous fluids were provided at 10 mL/kg/hr (Lactated Ringer’s solution; Baxter Healthcare Corporation, Chicago, IL, USA). An epidural using morphine (0.1 mg/kg;
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preservative-free morphine sulfate; Hospira, Lake Forest, IL, USA) and bupivacaine (1 mg/kg; Hospira, Lake Forest, IL, USA) was administered into the L6-L7 vertebral space. Anesthesia was maintained with isoflurane (0-2.5%) in oxygen via a 3.5mm Magill uncuffed endotracheal tube. Moderate hypotension was experienced during the procedure, which resolved with a fluid
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bolus (5 mL/kg Lactated Ringer’s solution intravenously) and the addition of a norepinephrine constant rate infusion (CRI) (0.3-0.5 mg/kg/min; Claris Lifescience Inc., North Brunswick, NJ, USA). Mild bradycardia was experienced twice during the procedure, which resolved with
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glycopyrrolate (0.005 mg/kg intravenously) each time.
The left pelvic limb was prepared for surgery using sterile technique. A coxofemoral amputation was performed as previously described in the literature.1 Following surgery, the sedation for anesthesia was reversed using flumazenil (0.02 mg/kg intravenously) and the
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patient recovered quickly. She was hypothermic following surgery (96.8 oF) but responded well
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to external heat support.
The morning following surgery, the rabbit’s temperature was normal and she was eating
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on her own. The next day she appeared lethargic, but was still eating with apparently adequate
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pain relief despite de-escalating pain therapy from injectable opioids to tramadol (10 mg/kg orally every twelve hours). At time of discharge she was found dead in her cage. A complete
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post-mortem examination was performed. Gross necropsy of the amputated limb revealed a 9.5 x 4 x 2 cm, moderately well-
demarcated mass in the subcutis of the lateral aspect of the tarsus/metatarsus that was freely moveable from the underlying skeletal muscle (Fig. 3A+B). A complete tissue set was fixed in 10% formalin, embedded in paraffin, sectioned at 5-µm-thick sections, stained routinely with
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hematoxylin and eosin (HE), and examined by a board-certified pathologist. Histological examination revealed an ulcerated, moderately cellular, invasive neoplasm with large, multifocal regions of necrosis and superficial bacterial infection. Neoplastic cells were arranged in long, loosely aggregated streams embedded in a moderate amount of loose, fibrillar stroma
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(Fig. 4). Neoplastic cells were spindloid with variably distinct margins, pale basophilic to
amphophilic cytoplasm, and oval nuclei with coarse chromatin and indistinct nucleoli. Cellular atypia and mitotic figures were rare. These features were considered diagnostic for a soft tissue
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sarcoma.
Additional histologic diagnoses included moderate cardiomyocyte degeneration and pulmonary alveolar histiocytosis, suggestive of possible mild left-sided congestive heart failure, which may have contributed to post-anesthetic death. The histologic correlate for the enlarged
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popliteal lymph node (seen on CT) was lymphoid hyperplasia and draining reaction; metastatic
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disease was not identified. Remaining findings were considered incidental. Immunohistochemical antigens including periaxin (Sigma, St. Louis, MO USA, anti-
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periaxin, HPA001868, 1:1000) and laminin (BioGenex, Fremont, CA USA, anti-laminin, PU078-
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UP, 1:40) were applied to the mass. Neoplastic cells had strong, cytoplasmic to membranous immunoreactivity to both antigens (Fig. 5). The immunohistochemical profile and
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histomorphology of this mass were considered diagnostic for a peripheral nerve sheath tumor.
Discussion
To the authors’ knowledge, this is the first complete case description of a peripheral nerve sheath tumor (PNST) in a rabbit confirmed using immunohistochemistry. PNSTs are soft
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tissue sarcomas that arise from components of the peripheral nervous system. They are generally divided into benign PNST (also called PNST), which may be subdivided into schwannoma, neurofibroma, or perineuroma, and a separate designation for malignant PNST.2 Malignant PNSTs are uncommon in veterinary species and histologic diagnosis requires
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substantial cellular atypia, aggressive local invasion, and/or definitive association with a peripheral nerve.2, 3
While PNSTs are relatively common in humans, malignant forms are rare, occurring in
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only 0.001% of the general population and accounting for approximately 6% of soft tissue
sarcomas.4, 5 PNSTs have also been described to date in a number of domestic species including dogs, cats, horses, cattle, goats, and pigs.2, 3 Although PNST has been reported in dermatologic and neurologic disease reviews in lagomorphs, detailed case descriptions are lacking.6, 7
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In dogs, PNSTs often develop in association with the trigeminal nerve, brachial plexus, or
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in the subcutis.8, 9 In cats, 75% of tumors involve the head, neck, or limbs.10 In a retrospective study of cutaneous neoplasms in pet rabbits, PNSTs were described in 8 out of 179 rabbits, with
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locations including the pinna, head, neck, axilla, thorax, abdomen, and limbs.6 These 8 rabbits
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were diagnosed with malignant PNSTs; histologic evaluation revealed well-demarcated proliferation and local invasion was not reported. 6
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Clinical signs of PNSTs depend on initial location of the tumor and are related to the underlying function of that location, such as lameness if located in the brachial plexus or facial paralysis if located in the trigeminal nerve.5, 9, 11 Diagnostic work-up may include bloodwork, radiographs, ultrasound, and advanced imaging such as CT or MRI.12 In regards to imaging, CT scan or MRI is typically recommended to determine extent of the mass as well as evaluate for
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metastatic disease, with MRI considered the superior option.9 On CT scan, PNSTs appear as a well-defined mass, however density is similar to muscle and there may be little to no contrast enhancement.11, 13 In the current case, CT was chosen as the family had elected for amputation and evaluation for metastatic disease was prioritized over evaluating the local behavior of the
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tumor. However, in cases in which PNST is suspected and evaluating local invasion is the priority of imaging, MRI should be the imaging modality of choice.
Diagnosis of PNSTs requires cytologic, histologic, and/or immunohistologic evaluation.
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Differentiating PNSTs from other spindle cell tumors can be challenging with histology alone and immunohistochemistry is often necessary to confirm a diagnosis.2 In veterinary species, this is especially important as distinct morphologic patterns are often not as readily apparent as in people, and PNSTs can be mistaken for other soft tissue sarcomas, such as rhabdomyosarcomas
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and hemangiopericytomas.14, 15 In the current case, the antibodies periaxin, which is specific to
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peripheral myelin, and laminin, specific to basement membrane producing cells, were both immunoreactive to neoplastic cells. While laminin is not specific for PNST, it is supportive of the
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diagnosis, and in combination with periaxin, is diagnostic for cells of peripheral nerve origin.
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The combination of this immunohistochemical profile and the histomorphology of the neoplastic spindle cells is considered diagnostic for a PNST. The histomorphology was most
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consistent with schwannoma with some Antoni B morphology (loosely aggregated cells in a loose matrix).2 Treatment options for PNSTs in rabbits can include chemotherapy and radiation
therapy, however primary excision of the mass is recommended if possible. Most cutaneous neoplasms that are surgically excised with good margins are reported to lead to curative
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outcomes.16 However, when size or location of the mass, or small size of the animal, make complete excision unlikely, radiation therapy may be an appropriate modality.16 Wide, complete excision followed by radiation therapy may be considered the ideal treatment.7, 16 Radiation therapy has achieved good results in several rabbit neoplasms; its role for PNSTs in
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rabbits is yet to be explored.12 Similarly, for non-resectable tumors, intralesional chemotherapy may be an option12. In the current case, amputation was the recommended therapy.
Amputation in rabbits is generally well-tolerated with a median overall survival time of 720 days
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in one retrospective study.17 However, caution should be given when electing for amputation in rabbits with pre-existing orthopedic or neurologic issues, obesity, or pododermatitis as these all lead to a greater rate of post-surgical complications.17 Despite the rabbit in the current case being both mildly overweight and having pododermatitis on all four limbs, amputation was
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elected given the rapidity of the tumor growth.
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Prognostic factors specific for PNST in rabbits have not been established, but generally soft tissue sarcomas in rabbits are typically locally aggressive with rapid growth, as seen in this
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case.16 Prognosis for survival and metastases in dogs with PNSTs is based on histologic grade
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and mitotic rate.18 Generally, canine PNSTs treated surgically with complete excision have a good prognosis. In cats, metastasis has not been documented with PNSTs, and any decline post-
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operatively is usually due to local recurrence.9, 10 A similar behavior has been reported in rabbits, with one report of persistent recurrence of the PNST despite multiple surgeries.6 In the current case, the neoplasm showed similarly aggressive local behavior and metastasis was not found on CT scan, gross necropsy, or histologic examination. Unfortunately, this rabbit was
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found dead seven weeks after diagnosis, an event that was not considered directly caused by PNST, and thus additional information on disease progression for this animal was unavailable. Further research is needed to evaluate underlying risk factors for PNST in rabbits. Much work remains in understanding the role and benefits of adjunctive therapy in rabbits with this
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neoplasm, especially in cases in which complete excision is not an option. Finally, better
delineating prognostic factors as well as determining long-term prognosis in lagomorphs will
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help to guide client and clinician decision making.
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Figures
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Figure 1 – Cytology from a fine needle aspirate of a mass on the left pelvic limb of a domestic rabbit. The background is bloody with free cell nuclei. The cells are spindle to stellate in shape with pale to medium blue and wispy cytoplasm and surrounded by pink material (matrix). Nuclear to cytoplasmic (N:C) ratios are high and anisocytosis and anisokaryosis are moderate. The chromatin pattern is finely stippled with multiple inconspicuous nucleoli. Small numbers of blood associated leukocytes are also noted throughout the sample. 50X magnification; red blood cells present in image are 6.7-6.9 um in diameter.19
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Figure 2 - Post IV contrast maximum intensity projection (MIP) image of the left pelvic limb of a domestic rabbit. There is a large, soft tissue attenuating, loculated, peripherally enhancing mass that extends from the caudal left stifle to the medial aspect of the distal left metatarsus. Proximally the mass has a tubular infiltrative extension dissecting between muscle bellies cranial to the gastrocnemius muscle. Distally at the level of the tarsus, there is a bulbous medial extension that is approximately 2.5 cm in at its greatest diameter. The underlying osseous structures are normal. The left popliteal lymph node is larger than the right.
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(a).
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(b). Figure 3 A+B – Gross images showing a 9.5 x 4 x 2 cm, moderately well-demarcated mass on the lateral aspect of the tarsus/metatarsus of a domestic rabbit. The mass is ulcerated and multifocally necrotic.
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Figure 4 – Histopathology of a peripheral nerve sheath tumor on the tarsus/metatarsus of a domestic rabbit. The mass is composed of loosely aggregated streams of neoplastic cells in a moderate amount of loose, fibrillar matrix. Neoplastic cells are spindloid with minimal cellular atypia. HE. 100x magnification.
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Figure 5 – Anti-laminin immunohistochemisty of a peripheral nerve sheath tumor on the pelvic limb of a domestic rabbit. Approximately 80% of neoplastic cells have linear, perimembranous to diffuse, cytoplasmic immunoreactivity (dotted arrows). Small caliber blood vessels with discontinuous membranous immunoreactivity (solid arrows) are used a positive internal control. 400x magnification.
Acknowledgements The authors wish to thank the histology staff at the University of California Davis (UCD) for technical support. The authors also thank Dr. Matthew Sheley of UCD for case consultation, as well as Dr. Sarah Woods of UCD for CT scan assessment.
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References [1] Higgins S, Guzman D, et al.: Coxofemoral amputation in a domestic rabbit (Oryctolagus cuniculus) with tibiofibular osteoblastic osteosarcoma. Journal of Exotic Pet Medicine 24: 455463, 2015. [2] Miller AD, Zachary JF: Nervous System, in Zachary JF, McGavin MD (ed): Pathologic basis of veterinary disease. St.Louis, Mo., Elsevier, pp 805-907, 2012. [3] Robert J. Higgins AWB, Peter J. Dickinson and Sílvia Sisó-Llonch: Ch. 19 Tumors of the Nervous System, in Meuten DJ (ed): Tumors in domestic animals. Ames, Iowa, John Wiley & Sons Inc., pp 834-891, 2017 [4] Yuan Z, Xu L, et al.: Clinicopathological features and prognosis of malignant peripheral nerve sheath tumor: a retrospective study of 159 cases from 1999 to 2016. Oncotarget 2017. [5] Huang JH, Zhang J, et al.: Diagnosis and treatment options for nerve sheath tumors. Expert Rev Neurother 5: 515-523, 2005. [6] von Bomhard W, Goldschmidt MH, et al.: Cutaneous neoplasms in pet rabbits: a retrospective study. Vet Pathol 44: 579-588, 2007. [7] Heatley JJ, Smith AN: Spontaneous neoplasms of lagomorphs. Vet Clin North Am Exot Anim Pract 7: 561-577, v, 2004. [8] Sawamoto O, Yamate J, et al.: A canine peripheral nerve sheath tumor including peripheral nerve fibers. J Vet Med Sci 61: 1335-1338, 1999. [9] McEntee MC, Dewey CW: Ch. 30 Tumors of the Nervous System, in Withrow SJ, Vail DM, Page RL (ed): Withrow & MacEwen's small animal clinical oncology. St. Louis, Missouri, Elsevier, pp 583-596, 2013 [10] Schulman FY, Johnson TO, et al.: Feline peripheral nerve sheath tumors: histologic, immunohistochemical, and clinicopathologic correlation (59 tumors in 53 cats). Vet Pathol 46: 1166-1180, 2009. [11] Kraft S, Ehrhart EJ, et al.: Magnetic resonance imaging characteristics of peripheral nerve sheath tumors of the canine brachial plexus in 18 dogs. Vet Radiol Ultrasound 48: 1-7, 2007. .[12] van Zeeland Y: Rabbit Oncology: Diseases, Diagnostics, and Therapeutics. Vet Clin North Am Exot Anim Pract 20: 135-182, 2017. [13] Carvalho MP, Fernandes NC, et al.: Benign Peripheral Nerve Sheath Tumor in a Wild Toco Toucan ( Ramphastos toco ). J Avian Med Surg 30: 280-285, 2016. [14] Chijiwa K, Uchida K, et al.: Immunohistochemical evaluation of canine peripheral nerve sheath tumors and other soft tissue sarcomas. Vet Pathol 41: 307-318, 2004. [15] Snyder LA, Linder KE, et al.: Malignant peripheral nerve sheath tumor in a hamster. J Am Assoc Lab Anim Sci 46: 55-57, 2007. [16] Kanfer S, Reavill DR: Cutaneous neoplasia in ferrets, rabbits, and guinea pigs. Vet Clin North Am Exot Anim Pract 16: 579-598, 2013. [17] Northrup NC, Barron GH, et al.: Outcome for client-owned domestic rabbits undergoing limb amputation: 34 cases (2000-2009). J Am Vet Med Assoc 244: 950-955, 2014. [18] Dennis MM, McSporran KD, et al.: Prognostic factors for cutaneous and subcutaneous soft tissue sarcomas in dogs. Vet Pathol 48: 73-84, 2011. [19] Weiss DJ, Wardrop KJ, et al.: Schalm's veterinary hematology. (6th). Ames, Iowa, WileyBlackwell, 2010.
Peripheral Nerve Sheath Tumor in the Pelvic Limb of a Domestic Rabbit (Oryctolagus cuniculus) Lauren Reimnitz DVM , David Sanchez-Migallon Guzman LV, MS, DECZM (Avian, Small Mammal), DACZM , Elise LaDouceur DVM, DACVP , Sarah Stevens DVM, MS , Noemie Summa Dr Med Vet, IPSAV (Zoological Medicine) , ´ Sara Gardhouse DVM , Amir Kol DVM, AVCP, PhD , Kelsey Brust DVM , Michelle G. Hawkins VMD, DABVP (Avian) PII: DOI: Reference:
S1557-5063(17)30292-6 https://doi.org/10.1053/j.jepm.2018.04.018 JEPM 50122
To appear in:
Journal of Exotic Pet Medicine
Received date: Revised date: Accepted date:
20 October 2017 31 December 2017 3 April 2018
Please cite this article as: Lauren Reimnitz DVM , David Sanchez-Migallon Guzman LV, MS, DECZM (Avian, Small Elise LaDouceur DVM, DACVP , Sarah Stevens DVM, MS , Noemie Summa Dr Med Vet, IPSAV (Zoological Medi ´ Sara Gardhouse DVM , Amir Kol DVM, AVCP, PhD , Kelsey Brust DVM , Michelle G. Hawkins VMD, DABVP (Avian) , Peripheral Nerve Sheath Tumor in the Pelvic Limb of a Domestic Rabbit (Oryctolagus cuniculus), Journal of Exotic Pet Medicine (2018), doi: https://doi.org/10.1053/j.jepm.2018.04.018
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Peripheral Nerve Sheath Tumor in the Pelvic Limb of a Domestic Rabbit (Oryctolagus cuniculus)
Lauren Reimnitz, DVM; David Sanchez-Migallon Guzman, LV, MS, DECZM (Avian, Small
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Mammal), DACZM; Elise LaDouceur, DVM, DACVP; Sarah Stevens, DVM, MS; Noémie Summa, Dr Med Vet, IPSAV (Zoological Medicine); Sara Gardhouse, DVM; Amir Kol, DVM, AVCP, PhD; Kelsey Brust, DVM; Michelle G. Hawkins, VMD, DABVP (Avian)
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From the Department of Medicine and Epidemiology (Sanchez-Migallon Guzman, Hawkins), William R. Pritchard Veterinary Medical Teaching Hospital (Summa, Gardhouse), Department of Pathology, Microbiology, and Immunology (LaDouceur, Stevens, Kol), and Department of
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Surgical and Radiological Sciences (Brust), School of Veterinary Medicine, University of
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California, Davis, One Shields Avenue, Davis, CA 95616
Corresponding author: David Sanchez-Migallon Guzman
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Department of Medicine and Epidemiology, School of Veterinary Medicine, University of
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California at Davis, One Shields Ave, 2108 Tupper Hall, Davis, CA 95616. Email: [email protected]
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Phone: (530) 752-1393 Fax: (530) 752-8906
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Peripheral Nerve Sheath Tumor in the Pelvic Limb of a Domestic Rabbit (Oryctolagus
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cuniculus)
Abstract
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A 3-year-old, 4.0 kg, female, spayed Silver Marten cross rabbit (Oryctolagus cuniculus) was presented for evaluation of a suspected recurring spindle cell sarcoma following primary excision by the referring veterinarian. Physical examination revealed a large subcutaneous mass on the left metatarsus and a fine needle aspirate revealed suspected neoplastic spindle cells.
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Hematologic evaluation was unremarkable and a computed tomography scan revealed invasion
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of the mass into skeletal muscles but showed no evidence of metastatic disease. An amputation was performed, after which the patient recovered uneventfully. However, the rabbit was found
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suddenly dead at time of discharge from unknown cause. Gross, histologic, and
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immunohistochemical evaluation was performed, which diagnosed a peripheral nerve sheath tumor. To the authors’ knowledge, this is the first detailed case report of a lagomorph
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peripheral nerve sheath tumor specifically confirmed with immunohistochemistry. Wide surgical excision is considered the treatment of choice and may be combined with radiation therapy. Further research is required to determine risk factors, the role of adjunctive therapy, as well as long term prognoses for peripheral nerve sheath tumors in rabbits. Key words
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Spindle cell sarcoma; lagomorph; amputation; metatarsus; neoplasia
Case description
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A 3-year-old, 4.0 kg, female, spayed Silver Marten cross rabbit (Oryctolagus cuniculus) was presented to the University of California Veterinary Medical Teaching Hospital (UCD; Davis, CA, USA) as a referral for a suspected recurring spindle cell sarcoma on her left pelvic limb.
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Previous history included pododermatitis, a right-sided head tilt, and a repaired abdominal hernia. A 3 x 6 cm, soft, fluctuant mass was noted on the medial aspect of her left metatarsus three and a half weeks prior to presentation at UCD. Mass removal was performed by the referring veterinarian one week later, at which time it was noted that the ventral aspect of the
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mass was infiltrating between metatarsal bones. The rabbit was discharged on enrofloxacin (10
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mg/kg orally every 12 hours; Bayer Healthcare, Shawnee Mission, KS, USA), and meloxicam (0.2 mg/kg orally every 12 hours; Metacam; Boehringer Ingelheim, Vetmedica, St. Joseph, MO, USA)
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and silver sulfadiazine cream (Ascend Laboratories, Montvale, NJ, USA) applied to the surgical
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site with daily bandage replacement. Histopathology revealed an incompletely excised spindle cell sarcoma.
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On presentation to UCD, physical examination findings revealed a fluctuant, 3 x 6 cm, subcutaneous mass deep to the previous surgical site. The remainder of the physical exam revealed a slight right-sided head tilt and grade I-II/VI pododermatitis on all limbs. A fine needle aspirate was performed and revealed suspected neoplastic spindle cells (Fig. 1). The client was
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advised to discontinue bandage changes and the current medications and a computed tomography (CT) scan was scheduled. On return examination three weeks later, the mass had increased in size to 9 x 5 x 3.5 cm with a 5 x 5 cm central ulcer. A complete blood count and chemistry panel were performed
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and were unremarkable. The next day, the rabbit was anesthetized for a whole-body CT scan with contrast. The CT scan revealed extension of the mass from the caudal left stifle to the medial aspect of the distal left metatarsus (~16 cm in length) (Fig. 2). Proximally, the mass
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invaded skeletal muscles without evidence of bone invasion/reaction. The left popliteal lymph node was enlarged to 1 x 0.5 cm. Imaging of the thorax and abdomen were unremarkable without evidence of metastatic disease. A limb amputation was scheduled for 8 days later. On return to UCD one day prior to surgery, the mass was multifocally necrotic, and the
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remainder of the physical examination was static. Bandages were changed daily in the hospital.
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Meloxicam and tramadol treatments continued, and the antibiotic was changed to chloramphenicol (50 mg/kg by mouth every 12 hours; Bimeda Inc., Le Sueur, MN).
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The following day the rabbit underwent a left coxofemoral amputation. Premedication
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was achieved with oxymorphone (0.2 mg/kg intramuscularly; Opana, Endo Pharmaceuticals Inc., Chadds Ford, PA, USA), midazolam (1 mg/kg intramuscularly), and glycopyrrolate (0.01
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mg/kg subcutaneously; West-Ward, Eatontown, NJ, USA). An IV catheter was placed and the rabbit was induced with ketamine (1.5 mg/kg intravenously; KetaVed, VedCo, St. Joseph, MO, USA) and midazolam (0.58 mg/kg intravenously), and oxymorphone (0.1 mg/kg intramuscularly). Intravenous fluids were provided at 10 mL/kg/hr (Lactated Ringer’s solution; Baxter Healthcare Corporation, Chicago, IL, USA). An epidural using morphine (0.1 mg/kg;
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preservative-free morphine sulfate; Hospira, Lake Forest, IL, USA) and bupivacaine (1 mg/kg; Hospira, Lake Forest, IL, USA) was administered into the L6-L7 vertebral space. Anesthesia was maintained with isoflurane (0-2.5%) in oxygen via a 3.5mm Magill uncuffed endotracheal tube. Moderate hypotension was experienced during the procedure, which resolved with a fluid
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bolus (5 mL/kg Lactated Ringer’s solution intravenously) and the addition of a norepinephrine constant rate infusion (CRI) (0.3-0.5 mg/kg/min; Claris Lifescience Inc., North Brunswick, NJ, USA). Mild bradycardia was experienced twice during the procedure, which resolved with
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glycopyrrolate (0.005 mg/kg intravenously) each time.
The left pelvic limb was prepared for surgery using sterile technique. A coxofemoral amputation was performed as previously described in the literature.1 Following surgery, the sedation for anesthesia was reversed using flumazenil (0.02 mg/kg intravenously) and the
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patient recovered quickly. She was hypothermic following surgery (96.8 oF) but responded well
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to external heat support.
The morning following surgery, the rabbit’s temperature was normal and she was eating
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on her own. The next day she appeared lethargic, but was still eating with apparently adequate
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pain relief despite de-escalating pain therapy from injectable opioids to tramadol (10 mg/kg orally every twelve hours). At time of discharge she was found dead in her cage. A complete
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post-mortem examination was performed. Gross necropsy of the amputated limb revealed a 9.5 x 4 x 2 cm, moderately well-
demarcated mass in the subcutis of the lateral aspect of the tarsus/metatarsus that was freely moveable from the underlying skeletal muscle (Fig. 3A+B). A complete tissue set was fixed in 10% formalin, embedded in paraffin, sectioned at 5-µm-thick sections, stained routinely with
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hematoxylin and eosin (HE), and examined by a board-certified pathologist. Histological examination revealed an ulcerated, moderately cellular, invasive neoplasm with large, multifocal regions of necrosis and superficial bacterial infection. Neoplastic cells were arranged in long, loosely aggregated streams embedded in a moderate amount of loose, fibrillar stroma
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(Fig. 4). Neoplastic cells were spindloid with variably distinct margins, pale basophilic to
amphophilic cytoplasm, and oval nuclei with coarse chromatin and indistinct nucleoli. Cellular atypia and mitotic figures were rare. These features were considered diagnostic for a soft tissue
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sarcoma.
Additional histologic diagnoses included moderate cardiomyocyte degeneration and pulmonary alveolar histiocytosis, suggestive of possible mild left-sided congestive heart failure, which may have contributed to post-anesthetic death. The histologic correlate for the enlarged
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popliteal lymph node (seen on CT) was lymphoid hyperplasia and draining reaction; metastatic
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disease was not identified. Remaining findings were considered incidental. Immunohistochemical antigens including periaxin (Sigma, St. Louis, MO USA, anti-
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periaxin, HPA001868, 1:1000) and laminin (BioGenex, Fremont, CA USA, anti-laminin, PU078-
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UP, 1:40) were applied to the mass. Neoplastic cells had strong, cytoplasmic to membranous immunoreactivity to both antigens (Fig. 5). The immunohistochemical profile and
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histomorphology of this mass were considered diagnostic for a peripheral nerve sheath tumor.
Discussion
To the authors’ knowledge, this is the first complete case description of a peripheral nerve sheath tumor (PNST) in a rabbit confirmed using immunohistochemistry. PNSTs are soft
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tissue sarcomas that arise from components of the peripheral nervous system. They are generally divided into benign PNST (also called PNST), which may be subdivided into schwannoma, neurofibroma, or perineuroma, and a separate designation for malignant PNST.2 Malignant PNSTs are uncommon in veterinary species and histologic diagnosis requires
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substantial cellular atypia, aggressive local invasion, and/or definitive association with a peripheral nerve.2, 3
While PNSTs are relatively common in humans, malignant forms are rare, occurring in
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only 0.001% of the general population and accounting for approximately 6% of soft tissue
sarcomas.4, 5 PNSTs have also been described to date in a number of domestic species including dogs, cats, horses, cattle, goats, and pigs.2, 3 Although PNST has been reported in dermatologic and neurologic disease reviews in lagomorphs, detailed case descriptions are lacking.6, 7
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In dogs, PNSTs often develop in association with the trigeminal nerve, brachial plexus, or
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in the subcutis.8, 9 In cats, 75% of tumors involve the head, neck, or limbs.10 In a retrospective study of cutaneous neoplasms in pet rabbits, PNSTs were described in 8 out of 179 rabbits, with
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locations including the pinna, head, neck, axilla, thorax, abdomen, and limbs.6 These 8 rabbits
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were diagnosed with malignant PNSTs; histologic evaluation revealed well-demarcated proliferation and local invasion was not reported. 6
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Clinical signs of PNSTs depend on initial location of the tumor and are related to the underlying function of that location, such as lameness if located in the brachial plexus or facial paralysis if located in the trigeminal nerve.5, 9, 11 Diagnostic work-up may include bloodwork, radiographs, ultrasound, and advanced imaging such as CT or MRI.12 In regards to imaging, CT scan or MRI is typically recommended to determine extent of the mass as well as evaluate for
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metastatic disease, with MRI considered the superior option.9 On CT scan, PNSTs appear as a well-defined mass, however density is similar to muscle and there may be little to no contrast enhancement.11, 13 In the current case, CT was chosen as the family had elected for amputation and evaluation for metastatic disease was prioritized over evaluating the local behavior of the
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tumor. However, in cases in which PNST is suspected and evaluating local invasion is the priority of imaging, MRI should be the imaging modality of choice.
Diagnosis of PNSTs requires cytologic, histologic, and/or immunohistologic evaluation.
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Differentiating PNSTs from other spindle cell tumors can be challenging with histology alone and immunohistochemistry is often necessary to confirm a diagnosis.2 In veterinary species, this is especially important as distinct morphologic patterns are often not as readily apparent as in people, and PNSTs can be mistaken for other soft tissue sarcomas, such as rhabdomyosarcomas
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and hemangiopericytomas.14, 15 In the current case, the antibodies periaxin, which is specific to
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peripheral myelin, and laminin, specific to basement membrane producing cells, were both immunoreactive to neoplastic cells. While laminin is not specific for PNST, it is supportive of the
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diagnosis, and in combination with periaxin, is diagnostic for cells of peripheral nerve origin.
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The combination of this immunohistochemical profile and the histomorphology of the neoplastic spindle cells is considered diagnostic for a PNST. The histomorphology was most
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consistent with schwannoma with some Antoni B morphology (loosely aggregated cells in a loose matrix).2 Treatment options for PNSTs in rabbits can include chemotherapy and radiation
therapy, however primary excision of the mass is recommended if possible. Most cutaneous neoplasms that are surgically excised with good margins are reported to lead to curative
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outcomes.16 However, when size or location of the mass, or small size of the animal, make complete excision unlikely, radiation therapy may be an appropriate modality.16 Wide, complete excision followed by radiation therapy may be considered the ideal treatment.7, 16 Radiation therapy has achieved good results in several rabbit neoplasms; its role for PNSTs in
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rabbits is yet to be explored.12 Similarly, for non-resectable tumors, intralesional chemotherapy may be an option12. In the current case, amputation was the recommended therapy.
Amputation in rabbits is generally well-tolerated with a median overall survival time of 720 days
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in one retrospective study.17 However, caution should be given when electing for amputation in rabbits with pre-existing orthopedic or neurologic issues, obesity, or pododermatitis as these all lead to a greater rate of post-surgical complications.17 Despite the rabbit in the current case being both mildly overweight and having pododermatitis on all four limbs, amputation was
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elected given the rapidity of the tumor growth.
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Prognostic factors specific for PNST in rabbits have not been established, but generally soft tissue sarcomas in rabbits are typically locally aggressive with rapid growth, as seen in this
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case.16 Prognosis for survival and metastases in dogs with PNSTs is based on histologic grade
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and mitotic rate.18 Generally, canine PNSTs treated surgically with complete excision have a good prognosis. In cats, metastasis has not been documented with PNSTs, and any decline post-
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operatively is usually due to local recurrence.9, 10 A similar behavior has been reported in rabbits, with one report of persistent recurrence of the PNST despite multiple surgeries.6 In the current case, the neoplasm showed similarly aggressive local behavior and metastasis was not found on CT scan, gross necropsy, or histologic examination. Unfortunately, this rabbit was
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found dead seven weeks after diagnosis, an event that was not considered directly caused by PNST, and thus additional information on disease progression for this animal was unavailable. Further research is needed to evaluate underlying risk factors for PNST in rabbits. Much work remains in understanding the role and benefits of adjunctive therapy in rabbits with this
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neoplasm, especially in cases in which complete excision is not an option. Finally, better
delineating prognostic factors as well as determining long-term prognosis in lagomorphs will
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help to guide client and clinician decision making.
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Figures
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Figure 1 – Cytology from a fine needle aspirate of a mass on the left pelvic limb of a domestic rabbit. The background is bloody with free cell nuclei. The cells are spindle to stellate in shape with pale to medium blue and wispy cytoplasm and surrounded by pink material (matrix). Nuclear to cytoplasmic (N:C) ratios are high and anisocytosis and anisokaryosis are moderate. The chromatin pattern is finely stippled with multiple inconspicuous nucleoli. Small numbers of blood associated leukocytes are also noted throughout the sample. 50X magnification; red blood cells present in image are 6.7-6.9 um in diameter.19
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Figure 2 - Post IV contrast maximum intensity projection (MIP) image of the left pelvic limb of a domestic rabbit. There is a large, soft tissue attenuating, loculated, peripherally enhancing mass that extends from the caudal left stifle to the medial aspect of the distal left metatarsus. Proximally the mass has a tubular infiltrative extension dissecting between muscle bellies cranial to the gastrocnemius muscle. Distally at the level of the tarsus, there is a bulbous medial extension that is approximately 2.5 cm in at its greatest diameter. The underlying osseous structures are normal. The left popliteal lymph node is larger than the right.
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(a).
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(b). Figure 3 A+B – Gross images showing a 9.5 x 4 x 2 cm, moderately well-demarcated mass on the lateral aspect of the tarsus/metatarsus of a domestic rabbit. The mass is ulcerated and multifocally necrotic.
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Figure 4 – Histopathology of a peripheral nerve sheath tumor on the tarsus/metatarsus of a domestic rabbit. The mass is composed of loosely aggregated streams of neoplastic cells in a moderate amount of loose, fibrillar matrix. Neoplastic cells are spindloid with minimal cellular atypia. HE. 100x magnification.
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Figure 5 – Anti-laminin immunohistochemisty of a peripheral nerve sheath tumor on the pelvic limb of a domestic rabbit. Approximately 80% of neoplastic cells have linear, perimembranous to diffuse, cytoplasmic immunoreactivity (dotted arrows). Small caliber blood vessels with discontinuous membranous immunoreactivity (solid arrows) are used a positive internal control. 400x magnification.
Acknowledgements The authors wish to thank the histology staff at the University of California Davis (UCD) for technical support. The authors also thank Dr. Matthew Sheley of UCD for case consultation, as well as Dr. Sarah Woods of UCD for CT scan assessment.
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References [1] Higgins S, Guzman D, et al.: Coxofemoral amputation in a domestic rabbit (Oryctolagus cuniculus) with tibiofibular osteoblastic osteosarcoma. Journal of Exotic Pet Medicine 24: 455463, 2015. [2] Miller AD, Zachary JF: Nervous System, in Zachary JF, McGavin MD (ed): Pathologic basis of veterinary disease. St.Louis, Mo., Elsevier, pp 805-907, 2012. [3] Robert J. Higgins AWB, Peter J. Dickinson and Sílvia Sisó-Llonch: Ch. 19 Tumors of the Nervous System, in Meuten DJ (ed): Tumors in domestic animals. Ames, Iowa, John Wiley & Sons Inc., pp 834-891, 2017 [4] Yuan Z, Xu L, et al.: Clinicopathological features and prognosis of malignant peripheral nerve sheath tumor: a retrospective study of 159 cases from 1999 to 2016. Oncotarget 2017. [5] Huang JH, Zhang J, et al.: Diagnosis and treatment options for nerve sheath tumors. Expert Rev Neurother 5: 515-523, 2005. [6] von Bomhard W, Goldschmidt MH, et al.: Cutaneous neoplasms in pet rabbits: a retrospective study. Vet Pathol 44: 579-588, 2007. [7] Heatley JJ, Smith AN: Spontaneous neoplasms of lagomorphs. Vet Clin North Am Exot Anim Pract 7: 561-577, v, 2004. [8] Sawamoto O, Yamate J, et al.: A canine peripheral nerve sheath tumor including peripheral nerve fibers. J Vet Med Sci 61: 1335-1338, 1999. [9] McEntee MC, Dewey CW: Ch. 30 Tumors of the Nervous System, in Withrow SJ, Vail DM, Page RL (ed): Withrow & MacEwen's small animal clinical oncology. St. Louis, Missouri, Elsevier, pp 583-596, 2013 [10] Schulman FY, Johnson TO, et al.: Feline peripheral nerve sheath tumors: histologic, immunohistochemical, and clinicopathologic correlation (59 tumors in 53 cats). Vet Pathol 46: 1166-1180, 2009. [11] Kraft S, Ehrhart EJ, et al.: Magnetic resonance imaging characteristics of peripheral nerve sheath tumors of the canine brachial plexus in 18 dogs. Vet Radiol Ultrasound 48: 1-7, 2007. .[12] van Zeeland Y: Rabbit Oncology: Diseases, Diagnostics, and Therapeutics. Vet Clin North Am Exot Anim Pract 20: 135-182, 2017. [13] Carvalho MP, Fernandes NC, et al.: Benign Peripheral Nerve Sheath Tumor in a Wild Toco Toucan ( Ramphastos toco ). J Avian Med Surg 30: 280-285, 2016. [14] Chijiwa K, Uchida K, et al.: Immunohistochemical evaluation of canine peripheral nerve sheath tumors and other soft tissue sarcomas. Vet Pathol 41: 307-318, 2004. [15] Snyder LA, Linder KE, et al.: Malignant peripheral nerve sheath tumor in a hamster. J Am Assoc Lab Anim Sci 46: 55-57, 2007. [16] Kanfer S, Reavill DR: Cutaneous neoplasia in ferrets, rabbits, and guinea pigs. Vet Clin North Am Exot Anim Pract 16: 579-598, 2013. [17] Northrup NC, Barron GH, et al.: Outcome for client-owned domestic rabbits undergoing limb amputation: 34 cases (2000-2009). J Am Vet Med Assoc 244: 950-955, 2014. [18] Dennis MM, McSporran KD, et al.: Prognostic factors for cutaneous and subcutaneous soft tissue sarcomas in dogs. Vet Pathol 48: 73-84, 2011. [19] Weiss DJ, Wardrop KJ, et al.: Schalm's veterinary hematology. (6th). Ames, Iowa, WileyBlackwell, 2010.