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Congenital Fetal Rhabdomyoma in a Thoroughbred Filly Foal
Journal of Equine Veterinary Science 36 (2016) 52–57
Contents lists available at ScienceDirect
Journal of Equine Veterinary Science journal homepage: www.j-evs.com
Case Report
Congenital Fetal Rhabdomyoma in a Thoroughbred Filly Foal Susan E. Keane a, *, Deborah J. Racklyeft b, David P. Taylor c a
Dartbrook Equine Veterinary Clinic, Scone, New South Wales, Australia Equine Medicine Consulting, Scone, New South Wales, Australia c Vetnostics, North Ryde, New South Wales, Australia b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 25 July 2015 Received in revised form 19 October 2015 Accepted 21 October 2015 Available online 29 October 2015
A Thoroughbred filly foal was presented 12 hours after birth for evaluation of a cranioventral cervical mass. A congenital tumor was suspected after ultrasound examination, fine needle aspirate, and biopsy of the mass. Desmin immunohistochemistry on a section of the mass after surgical excision confirmed a diagnosis of fetal rhabdomyoma, a rare congenital tumor only reported once before in a foal. In the short term, wound complications occurred, but the filly had no long-term complications and subsequently raced successfully. This report outlines the differential diagnoses for cranioventral cervical masses in the foal, the approach to diagnosis, and outlines the difficulties encountered in the removal of masses in this region. Ó 2015 Elsevier Inc. All rights reserved.
Keywords: Horse Cervical mass Rhabdomyoma Congenital tumor
1. Introduction
2. Case Details
Rhabdomyomas are benign mesenchymal tumors of skeletal muscle origin [1]. They have been categorized as cardiac or extracardiac types in human medicine [2]. In veterinary medicine, cardiac types have been commonly documented in pigs [3] and a case has also been documented in a fallow deer [4]. Extracardiac rhabdomyomas are further classified into four types: adult, fetal, genital, and rhabdomyomatous mesenchymal hamartoma [2]. In man, fetal rhabdomyoma is a rare tumor, usually occurring in the first 3 years of life and may be congenital [2,5]. Fetal type is typically seen in young boys in the subcutis and subdermis in the head and neck region [2]. A single case of a congenital fetal rhabdomyoma, presenting as a proximal ventral cervical mass, has been described in an Appaloosa filly foal [6]. The current report describes the presentation of a fetal rhabdomyoma in a Thoroughbred foal and its successful surgical treatment.
2.1. History A Thoroughbred filly foal was presented for examination 12 hours after birth because a ventral cervical swelling had been noted by the owners. The foal was born at term after a normal gestation and parturition. No abnormalities were evident on the remainder of the clinical examination besides a firm mass in the upper third of the ventral cervical region. The mass was approximately 5 cm 7 cm 2 cm in size and was well circumscribed (Fig. 1). It was nonpainful and freely moveable within the subcutaneous space except for a projection to the left of midline that felt attached to deeper structures. Differential diagnoses included a branchial remnant cyst, hematoma, seroma, goiter, a vascular anomaly such as a hemangioma, hamartoma, teratoma, or other congenital tumor. 2.2. Diagnostics
* Corresponding author at: Susan E. Keane, Dartbrook Equine Veterinary Clinic, 410 Bunnan Rd, Scone, New South Wales 2337, Australia. E-mail address: [email protected] (S.E. Keane). 0737-0806/$ – see front matter Ó 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jevs.2015.10.009
Serum hematology and biochemistry were performed. No significant abnormalities were evident. A glutaraldehyde
S.E. Keane et al. / Journal of Equine Veterinary Science 36 (2016) 52–57
53
moderate basophilic ground substance. The cells in the intervening tissue occasionally had a stellate appearance. Mitotic figures were not obvious. A juvenile mesenchymal tumor was suspected, with differential diagnoses including juvenile hemangioma or hemangioendothelioma. Immunohistochemistry was recommended and performed on the same sample to differentiate more exactly what type of tumor was present. The mesenchymal cells stained strongly with vimentin (mesenchymal marker) and failed to stain with smooth muscle actin (smooth muscle marker) and factor 8 (endothelial marker), ruling out hemangioma. A tumor of skeletal muscle origin or a juvenile hemangioendothelioma was suspected. As the foal was clinically normal, time was given in case of spontaneous regression, which has been documented in humans with congenital fibromatosis [7]. In the 3 weeks after biopsy, however, the mass rapidly increased in size and surgical removal was performed.
Fig. 1. Photograph of Thoroughbred filly foal at 4 weeks of age. A wellcircumscribed mass approximately 5 cm 7 cm 2 cm in size is visible on the ventral aspect of the neck. The mass was not associated with the thyroid gland.
2.3. Surgery
coagulation test was performed on the farm for assessment of adequacy of passive transfer of colostral IgG and was found to be normal. An ultrasound examination was performed using a 7.5to 12-MHz linear probe. The mass was heterogeneous and hyperechoic, measuring 5 cm 2 cm 7 cm in size, 6 cm distal to the ramus of the mandible, and not associated with the thyroid gland. No cystic or fluid-filled structures were noted (Figs. 2A and 2B). Ultrasound examination findings of a solid, soft tissue mass ruled out hematoma, seroma, or branchial remnant cyst as differentials. The revised diagnosis was a congenital tumor. As the foal was clinically normal, no further diagnostics were undertaken until the foal was older. At 1 month of age, no change in the size of the mass had occurred and further diagnostics were pursued. A fine needle aspirate (FNA) was initially performed. The foal was sedated using butorphanol (Butorgesic) (Troy ilium, Glendenning, New South Wales, Australia) 0.04 mg/kg IV and xylazine (Ilium Xylazil) (Troy ilium, Glendenning, New South Wales, Australia) 0.3 mg/kg IV. The mass was clipped and an area aseptically prepared. A FNA of the mass was taken. Slides were prepared stall side and sent to an outside laboratory for examination. Results were diagnostically inconclusive, and a preliminary diagnosis of a spindle cell tumor was suggested. A week later, a manual biopsy of the mass was performed under ultrasound guidance. The foal was sedated with xylazine 0.3 mg/kg IV and butorphanol 0.04 mg/kg IV. The area was aseptically prepared, and 0.5 mL of lignocaine hydrochloride (Ilium Lignocaine 20) (Troy ilium, Glendenning, New South Wales, Australia) was injected subcutaneously. A biopsy was taken using a 14 g 15 cm tru-cut biopsy needle (CareFusion, McGaw Park, IL, USA). Samples were fixed in 10% formalin and sent for histopathological analysis. Histopathology revealed an abnormal proliferation of small uniform spindle cells, frequently forming collapsed capillaries and arranged in irregular sheets among
The foal was placed under general anesthesia. A 20-cm ventral midline skin incision was made over the mass, and a combination of blunt and sharp dissection was used to mobilize it. It was firm, well circumscribed, and measured 20 12 12 cm. It extended along fascial planes and was deeply attached to the soft tissues dorsolateral to the left side of the trachea, near the carotid artery. In addition, the left brachiocephalic muscle was incorporated in the left lateral aspect of the mass. The carotid artery and vagosympathetic trunk were identified, and care was taken to avoid manipulation and damage during surgery. Three large arterial branches from the carotid artery that were supplying the tumor were ligated. Two associated nerve branches were transected as close to the mass as possible. This was done to avoid damage to the vagosympathetic trunk. Tumor removal resulted in a large amount of dead space. A Penrose drain was placed extending through the deep layers to exit through separate incisions proximal and distal to the skin wound. The incision was closed in three layers using three metric polydioxanone (Ethicon Products, Johnson & Johnson Medical, North Ryde, New South Wales, Australia) in a simple interrupted pattern and two metric polydioxanone (Ethicon Products, Johnson & Johnson Medical, North Ryde, New South Wales, Australia) in a simple continuous pattern. The skin incision was closed with staples, and a sterile padded dressing was applied. The foal recovered uneventfully from anesthesia. The filly was treated with procaine penicillin (Propercillin) (Troy ilium, Glendenning, New South Wales, Australia) 22 mg/kg IM q12 hours and gentamicin (Gentam 100) (Troy ilium, Glendenning, New South Wales, Australia) 6.6 mg/kg IV q24 hours for 5 days after surgery. Flunixin meglumine (Flunixon) (Norbrook, Australasia Pty, Tullamarine, Victoria, Australia) 1.1 mg/kg IV q12 hours was continued for 2 days after surgery. After 2 days, anti-inflammatory treatment was changed to phenylbutazone (Butin paste) (International Animal Health Products, Newmarket, New Zealand) 2.2 mg/kg per os q12 hours for 5 days. After 5 days, phenylbutazone was discontinued and antimicrobial
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Fig. 2. Ultrasound images of the cervical mass in (A) sagittal plane and (B) transverse plane. A heterogeneous soft tissue mass is visible, closely associated with the trachea.
therapy was changed to a trimethoprim-potentiated sulphonamide (Sulprim) (Troy ilium, Glendenning, New South Wales, Australia) 30 mg/kg per os q12 hours. The filly was monitored carefully postoperatively for signs of Horner’s syndrome, dysphagia, and development of aspiration pneumonia. 2.4. Gross Pathology and Histopathology The mass was examined after removal. It was heterogeneous and lobulated and well circumscribed except for the two areas of attachment described previously. The cut surface differed in color with some dark red areas, whereas other areas were pale yellow/grey. Some cystic areas with serous fluid were also noted (Fig. 3). Samples were taken from the mass, formalin fixed and sent for further histopathological analysis. On histopathology, some cells were streaming, whereas others had
Fig. 3. Gross appearance of mass after removal.
the appearance of strap cells with abundant trailing eosinophilic cytoplasm and very faint cross-striations. The striations in the cytoplasm of some of the streaming cells were suggestive of striated muscle. Desmin immunohistochemistry was used on samples taken at surgery to refine the diagnosis. The neoplastic cells including streaming, strap forms, those with crossstriations, and other loosely arranged cells were all labeled with desmin, confirming the fact that they were of skeletal muscle origin (Fig. 4). 2.5. Postoperative Care and Outcome After surgery, there was initially a large volume of serosanguinous discharge from the drains, which reduced
Fig. 4. Histological appearance of the cervical mass that was confirmed to be a fetal rhabdomyoma. Notice the spindle to strap cells with eosinophilic cytoplasm and occasional cross-striations. Hematoxylin and eosin stain. Bar ¼ 50 mm. Inset: desmin immunolabeling with cross-striations (arrow). Same magnification.
S.E. Keane et al. / Journal of Equine Veterinary Science 36 (2016) 52–57
after 72 hours. Five days postoperatively, however, increased purulent discharge was noted. A swab of the distal wound was taken for microbiological culture and sensitivity. Culture yielded a mixed growth with no predominant isolate. The Penrose drains were left in situ to allow continuing drainage. The wound was lavaged with several liters 0.5% povidone iodine (Apex Laboratories, Somersby, New South Wales, Australia) in 0.9% sodium chloride (Baxter Healthcare, Old Toongabbie, New South Wales, Australia) solution twice daily. To provide protection, a Lycra hood was applied to cover the incision. Twice daily dressing, changes were carried out using a dry absorbent dressing. The swelling reduced within 72 hours, and the exudate reduced gradually over a period of 12 days. On day 12, the drain and skin staples were removed, antibiotic therapy was discontinued, and the foal was discharged. Three weeks postoperatively, all discharge had stopped (Fig. 5A). Some soft tissue thickening was still evident, which resolved over several months. Because of concerns about possible surgical damage to the vagosympathetic trunk, the foal was monitored carefully for development of dysphagia and pneumonia. Upper airway endoscopy was performed 3 months postoperatively and was within normal limits (grade 1, Lane et al). After 12 months, no recurrence or complications had occurred. The filly was sold at public auction (Fig. 5B) and has successfully raced. 3. Discussion Differential diagnoses for proximal cervical masses in the horse include branchial apparatus anomalies (such as branchial remnant cysts) [8], congenital goiter [9], tumors (teratoma, hemangioma, rhabdomyoma, and hamartoma), retropharyngeal abscesses masses, and parotid salivary gland disease [10]. Branchial remnant cysts typically
55
present as a right-sided or dorsal retropharyngeal mass [11]. Congenital vascular tumors and hamartomas are relatively common in foals, but these usually occur as cutaneous nodules [12]. A single case of a subcutaneous fibrous hamartoma has been documented in a foal, which was situated on the lateral aspect of the neck [13]. Other congenital tumors such as teratomas may also occur in the neck region. In man, the neck is the second most common location for teratomas after the sacrum [14]. Ultrasonography is a useful diagnostic aid in differentiation of ventral cervical masses. Branchial remnant cysts have a thick, discrete wall, containing hypoechoic fluid with dependent hyperechoic masses visible [11]. In contrast, soft tissue tumors are likely to be homogenous in appearance. A FNA or biopsy of the mass is necessary for complete diagnosis. A fine needle aspirate is a simple, noninvasive technique commonly used in the diagnosis of head and neck tumors in man [15]. Cytomorphologically, rhabdomyoma tumor cells have eosinophilic finely granular cytoplasm, which can mimic other tumors [16], and misinterpretation of FNA results has been reported in cases of adult rhabdomyoma. Histologically, fetal rhabdomyomas are composed of immature striated muscle at the 6th to 10th week stage of development [17]. Two forms of fetal rhabdomyoma are recognized: myxoid and intermediate types [2]. Histologically, the myxoid type is composed of primitive oval or spindle-shaped cells haphazardly arranged in a myxoid stroma. The intermediate type is more common in adults and generally consists of cells with a greater degree of skeletal muscle differentiation [18,19]. This report found both FNA and tru-cut biopsy results to be inconclusive, highlighting the potential limitations of these procedures, due to small sample size. Immunohistochemical staining for desmin, vimentin, myoglobin, and muscle-specific actin has been used to
Fig. 5. Postoperative follow-up. (A) 21 days post operatively. (B) 12 months post operatively.
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differentiate congenital tumors [18,20]. Desmin is an intermediate filament in a subunit of intermediate filaments in skeletal muscle tissue, smooth muscle tissue, and cardiac muscle tissue. Vimentin, also an intermediate filament protein, is expressed in mesenchymal cells and is used as a nonspecific mesenchymal marker. Fetal rhabdomyoma typically stains for desmin, myoglobin, and muscle-specific actin in mature striated cells. Focal or rare staining for vimentin and smooth muscle actin is seen in primitive cells [19]. In contrast, adult rhabdomyoma is composed of comparatively mature cells that will not stain for vimentin [21]. In man, the recommended treatment for fetal rhabdomyoma is complete surgical excision [18]. Cases of recurrence have been documented in man, attributable to incomplete removal [22]. As results of FNA and tru-cut biopsy were suggestive of a benign mesenchymal tumor, time was given in case of spontaneous regression, which has been reported in cases of some congenital mesenchymal tumors [7]. Complications of surgical excision of masses in the neck region of the horse are divided into three major categories: vascular complications, nerve complications, and wound complications. The recurrent laryngeal nerve can be damaged from direct surgical trauma or secondary to cellulitis and inflammation postoperatively, leading to laryngeal hemiplegia [23]. Laryngeal hemiplegia was seen after branchial cyst resection in 80% of cases, indicating that even with careful dissection around a mass in the proximal cervical region there is a high risk of damage to local neurovascular structures [8]. Other neurovascular structures that may be damaged due to their close proximity include the jugular vein, carotid artery, and vagosympathetic trunk [24]. Transient dysphagia may also be encountered postoperatively [8]. Wound complications in this case occurred as a result of excessive dead space. Dead space results in accumulation of blood and serum, which reduces healing and provides a medium for bacterial proliferation [25]. The top and bottom of wound also varies with head position, and movement of subcutaneous tissues drags skin contaminants in as the horse moves its neck [26]. Bandages are difficult to apply and maintain in this site also due to movement, resulting in contamination of the surgical site. Drains facilitate the debridement phase of healing by providing a means of cellular debris removal. Penrose drains are inexpensive and easy to place and provide good passive drainage [25]. Most commonly they are used as a single exit drain; however, a double exit technique, as used in this report, is advised for neck wounds [26]. With this technique, one end exits the proximal aspect of the wound and the other exits distally. The advantage of this technique in the ventral neck region is that drainage occurs whether the neck is in flexion, neutral, or extended. If drainage persists or increases, a foreign body response should be suspected and the drain removed [25]. Prophylactic antibiotic administration is rarely indicated in the management of open wounds [27]. Postoperative antimicrobials were used in this case as there was concern that wound contamination would develop when using a passive open drainage technique for management of such a large and deep area of dead space.
Antimicrobial concentrations may have been inadequate to inactivate biofilm organisms that could have potentially colonized the drain used in this case, thus potentially selecting for resistant subpopulations of bacteria [28]. With the increasing incidence of antimicrobial resistance, the judicious use of antimicrobials is advocated in veterinary practice [29]. Thus, in retrospect, the authors feel that local wound management alone may have been equally successful in this case. 4. Conclusions Fetal rhabdomyoma should be considered as a differential diagnosis in horses with proximal ventral cervical masses. Immunohistochemistry is required for diagnosis. Prognosis for recovery is excellent after surgical excision, as demonstrated in this case. As with all surgeries in this region, complications are common and care must be taken to avoid damage to neurovascular structures and manage postoperative dead space.
References [1] Yalsangi S, Srinivasmurthy P, Jayalekshmy R, Maloth S, Ramadoss T, Kalladka M. Rhabdomyoma of the orofacial region. Hong Kong Dent J 2011;8:111–5. [2] Hansen T, Katenkamp D. Rhabdomyoma of the head and neck: morphology and differential diagnosis. Virchows Arch 2005;447: 849–54. [3] Omar AR. Congenital cardiac rhabdomyoma in a pig. Pathol Vet 1969;6:469–74. [4] Kolly C, Bidaut A, Robert N. Cardiac rhabdomyoma in a juvenile fallow deer (Dama dama). J Wildl Dis 2004;40:603–6. [5] Dehner LP, Enzinger FM, Font RL. Fetal rhabdomyoma. An analysis of nine cases. Cancer 1972;30:160–6. [6] Meyerholz DK, Caston SS, Haynes JS. Congenital fetal rhabdomyoma in a foal. Vet Pathol 2004;41:518–20. [7] Schaffzin EA, Chung SMK, Kaye R. Congenital generalized fibromatosis with complete spontaneous regression. J Bone Joint Surg Am 1972;54:657–62. [8] Nolen-Walston RD, Parente EJ, Madigan JE, David F, Knafo SE, Engiles JB. Branchial remnant cysts of mature and juvenile horses. Equine Vet J 2009;41:918–23. [9] Durham AE. Congenital goitre in two colt foals born to mares fed excess iodine during pregnancy. Equine Vet Educ 1995;7:239–41. [10] Elce Y. Thyroid masses and their causes. Equine Vet Educ 2014; 26:248–9. [11] Slovis NM, Watson JL, Couto SS. Marsupialization and iodine sclerotherapy of a branchial cyst in a horse. J Am Vet Med Assoc 2001;219:338–40. [12] Jabara AG, Hazard GH, O’Shea JD. A congenital vascular naevus in a foal. Aust Vet J 1984;61:286–8. [13] Collins N, Kelly G, Pollock PJ, McAllister H, Schumacher J. Subcutaneous fibrous hamartoma in a foal. Vet Rec 2004;154:474–6. [14] Carr MM, Thorner P, Phillips JH. Congenital teratomas of the head and neck. J Otolaryngol 1997;26:246–52. [15] Fulciniti F, Califano L, Zupi A, Vetrani A. Accuracy of fine needle aspiration biopsy in head and neck tumors. J Oral Maxillofac Surg 1997;55:1094–7. [16] Limbach AL, Goyal A. Adult rhabdomyoma: a challenging diagnosis on cytology. Cytojournal 2012;9:20. [17] Walsh SN, Hurt MA. Cutaneous fetal rhabdomyoma: a case report and historical review of the literature. Am J Surg Pathol 2008;32: 485–91. [18] Wan WK, Sng TY, Goh HK, Hwang SG. Foetal rhabdomyoma with fine-needle aspirate cytology correlation. Singapore Med J 2009;50: e138. [19] Kapadia SB, Meis JM, Frisman DM, Ellis GL, Heffner DK, Hyams VJ. Fetal rhabdomyoma of the head and neck: a clinicopathologic and immunophenotypic study of 24 cases. Hum Pathol 1993;24: 754–65.
S.E. Keane et al. / Journal of Equine Veterinary Science 36 (2016) 52–57 [20] Helliwell TR, Sissons MC, Stoney PJ, Ashworth MT. Immunochemistry and electron microscopy of head and neck rhabdomyoma. J Clin Pathol 1988;41:1058–63. [21] Jin B, Saleh H. Pitfalls in the diagnosis of adult rhabdomyoma by fine needle aspiration: report of a case and a brief literature review. Diagn Cytopathol 2009;37:483–6. [22] Valdez TA, Desai U, Volk MS. Recurrent fetal rhabdomyoma of the head and neck. Int J Pediatr Otorhinolaryngol 2006;70: 1115–8. [23] Stick JA. Surgery of the oesophagus. Vet Clin North Am Large Anim Pract 1982;4:33–59. [24] Green SL, Cochrane SM, Smith-Maxie L. Horner’s syndrome in ten horses. Can Vet J 1992;33:330–3.
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[25] Southwood LL. Wound management in hospitalized horses. In: Corley K, Stephen J, editors. The equine hospital manual30. Oxford: Blackwell Publishing Ltd; 2008. p. 609–23. [26] Stashak TS. Management of wounds of the neck or body. In: Stashak TS, Theoret CL, editors. Equine wound management. Hoboken: Wiley-Blackwell Ltd; 2008. p. 333–72. [27] Fowler D. Closed suction drains: options and applications. In: Proc North Am Vet Conf 2006;20:1463. [28] Donlan RM. Biofilms and device-associated infections. Emerg Infect Dis 2001;7:277–81. [29] Hughes LA, Pinchbeck G, Callaby R, Dawson S, Clegg P, Williams N. Antimicrobial prescribing practice in UK equine veterinary practice. Equine Vet J 2013;45:141–7.
Contents lists available at ScienceDirect
Journal of Equine Veterinary Science journal homepage: www.j-evs.com
Case Report
Congenital Fetal Rhabdomyoma in a Thoroughbred Filly Foal Susan E. Keane a, *, Deborah J. Racklyeft b, David P. Taylor c a
Dartbrook Equine Veterinary Clinic, Scone, New South Wales, Australia Equine Medicine Consulting, Scone, New South Wales, Australia c Vetnostics, North Ryde, New South Wales, Australia b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 25 July 2015 Received in revised form 19 October 2015 Accepted 21 October 2015 Available online 29 October 2015
A Thoroughbred filly foal was presented 12 hours after birth for evaluation of a cranioventral cervical mass. A congenital tumor was suspected after ultrasound examination, fine needle aspirate, and biopsy of the mass. Desmin immunohistochemistry on a section of the mass after surgical excision confirmed a diagnosis of fetal rhabdomyoma, a rare congenital tumor only reported once before in a foal. In the short term, wound complications occurred, but the filly had no long-term complications and subsequently raced successfully. This report outlines the differential diagnoses for cranioventral cervical masses in the foal, the approach to diagnosis, and outlines the difficulties encountered in the removal of masses in this region. Ó 2015 Elsevier Inc. All rights reserved.
Keywords: Horse Cervical mass Rhabdomyoma Congenital tumor
1. Introduction
2. Case Details
Rhabdomyomas are benign mesenchymal tumors of skeletal muscle origin [1]. They have been categorized as cardiac or extracardiac types in human medicine [2]. In veterinary medicine, cardiac types have been commonly documented in pigs [3] and a case has also been documented in a fallow deer [4]. Extracardiac rhabdomyomas are further classified into four types: adult, fetal, genital, and rhabdomyomatous mesenchymal hamartoma [2]. In man, fetal rhabdomyoma is a rare tumor, usually occurring in the first 3 years of life and may be congenital [2,5]. Fetal type is typically seen in young boys in the subcutis and subdermis in the head and neck region [2]. A single case of a congenital fetal rhabdomyoma, presenting as a proximal ventral cervical mass, has been described in an Appaloosa filly foal [6]. The current report describes the presentation of a fetal rhabdomyoma in a Thoroughbred foal and its successful surgical treatment.
2.1. History A Thoroughbred filly foal was presented for examination 12 hours after birth because a ventral cervical swelling had been noted by the owners. The foal was born at term after a normal gestation and parturition. No abnormalities were evident on the remainder of the clinical examination besides a firm mass in the upper third of the ventral cervical region. The mass was approximately 5 cm 7 cm 2 cm in size and was well circumscribed (Fig. 1). It was nonpainful and freely moveable within the subcutaneous space except for a projection to the left of midline that felt attached to deeper structures. Differential diagnoses included a branchial remnant cyst, hematoma, seroma, goiter, a vascular anomaly such as a hemangioma, hamartoma, teratoma, or other congenital tumor. 2.2. Diagnostics
* Corresponding author at: Susan E. Keane, Dartbrook Equine Veterinary Clinic, 410 Bunnan Rd, Scone, New South Wales 2337, Australia. E-mail address: [email protected] (S.E. Keane). 0737-0806/$ – see front matter Ó 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jevs.2015.10.009
Serum hematology and biochemistry were performed. No significant abnormalities were evident. A glutaraldehyde
S.E. Keane et al. / Journal of Equine Veterinary Science 36 (2016) 52–57
53
moderate basophilic ground substance. The cells in the intervening tissue occasionally had a stellate appearance. Mitotic figures were not obvious. A juvenile mesenchymal tumor was suspected, with differential diagnoses including juvenile hemangioma or hemangioendothelioma. Immunohistochemistry was recommended and performed on the same sample to differentiate more exactly what type of tumor was present. The mesenchymal cells stained strongly with vimentin (mesenchymal marker) and failed to stain with smooth muscle actin (smooth muscle marker) and factor 8 (endothelial marker), ruling out hemangioma. A tumor of skeletal muscle origin or a juvenile hemangioendothelioma was suspected. As the foal was clinically normal, time was given in case of spontaneous regression, which has been documented in humans with congenital fibromatosis [7]. In the 3 weeks after biopsy, however, the mass rapidly increased in size and surgical removal was performed.
Fig. 1. Photograph of Thoroughbred filly foal at 4 weeks of age. A wellcircumscribed mass approximately 5 cm 7 cm 2 cm in size is visible on the ventral aspect of the neck. The mass was not associated with the thyroid gland.
2.3. Surgery
coagulation test was performed on the farm for assessment of adequacy of passive transfer of colostral IgG and was found to be normal. An ultrasound examination was performed using a 7.5to 12-MHz linear probe. The mass was heterogeneous and hyperechoic, measuring 5 cm 2 cm 7 cm in size, 6 cm distal to the ramus of the mandible, and not associated with the thyroid gland. No cystic or fluid-filled structures were noted (Figs. 2A and 2B). Ultrasound examination findings of a solid, soft tissue mass ruled out hematoma, seroma, or branchial remnant cyst as differentials. The revised diagnosis was a congenital tumor. As the foal was clinically normal, no further diagnostics were undertaken until the foal was older. At 1 month of age, no change in the size of the mass had occurred and further diagnostics were pursued. A fine needle aspirate (FNA) was initially performed. The foal was sedated using butorphanol (Butorgesic) (Troy ilium, Glendenning, New South Wales, Australia) 0.04 mg/kg IV and xylazine (Ilium Xylazil) (Troy ilium, Glendenning, New South Wales, Australia) 0.3 mg/kg IV. The mass was clipped and an area aseptically prepared. A FNA of the mass was taken. Slides were prepared stall side and sent to an outside laboratory for examination. Results were diagnostically inconclusive, and a preliminary diagnosis of a spindle cell tumor was suggested. A week later, a manual biopsy of the mass was performed under ultrasound guidance. The foal was sedated with xylazine 0.3 mg/kg IV and butorphanol 0.04 mg/kg IV. The area was aseptically prepared, and 0.5 mL of lignocaine hydrochloride (Ilium Lignocaine 20) (Troy ilium, Glendenning, New South Wales, Australia) was injected subcutaneously. A biopsy was taken using a 14 g 15 cm tru-cut biopsy needle (CareFusion, McGaw Park, IL, USA). Samples were fixed in 10% formalin and sent for histopathological analysis. Histopathology revealed an abnormal proliferation of small uniform spindle cells, frequently forming collapsed capillaries and arranged in irregular sheets among
The foal was placed under general anesthesia. A 20-cm ventral midline skin incision was made over the mass, and a combination of blunt and sharp dissection was used to mobilize it. It was firm, well circumscribed, and measured 20 12 12 cm. It extended along fascial planes and was deeply attached to the soft tissues dorsolateral to the left side of the trachea, near the carotid artery. In addition, the left brachiocephalic muscle was incorporated in the left lateral aspect of the mass. The carotid artery and vagosympathetic trunk were identified, and care was taken to avoid manipulation and damage during surgery. Three large arterial branches from the carotid artery that were supplying the tumor were ligated. Two associated nerve branches were transected as close to the mass as possible. This was done to avoid damage to the vagosympathetic trunk. Tumor removal resulted in a large amount of dead space. A Penrose drain was placed extending through the deep layers to exit through separate incisions proximal and distal to the skin wound. The incision was closed in three layers using three metric polydioxanone (Ethicon Products, Johnson & Johnson Medical, North Ryde, New South Wales, Australia) in a simple interrupted pattern and two metric polydioxanone (Ethicon Products, Johnson & Johnson Medical, North Ryde, New South Wales, Australia) in a simple continuous pattern. The skin incision was closed with staples, and a sterile padded dressing was applied. The foal recovered uneventfully from anesthesia. The filly was treated with procaine penicillin (Propercillin) (Troy ilium, Glendenning, New South Wales, Australia) 22 mg/kg IM q12 hours and gentamicin (Gentam 100) (Troy ilium, Glendenning, New South Wales, Australia) 6.6 mg/kg IV q24 hours for 5 days after surgery. Flunixin meglumine (Flunixon) (Norbrook, Australasia Pty, Tullamarine, Victoria, Australia) 1.1 mg/kg IV q12 hours was continued for 2 days after surgery. After 2 days, anti-inflammatory treatment was changed to phenylbutazone (Butin paste) (International Animal Health Products, Newmarket, New Zealand) 2.2 mg/kg per os q12 hours for 5 days. After 5 days, phenylbutazone was discontinued and antimicrobial
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S.E. Keane et al. / Journal of Equine Veterinary Science 36 (2016) 52–57
Fig. 2. Ultrasound images of the cervical mass in (A) sagittal plane and (B) transverse plane. A heterogeneous soft tissue mass is visible, closely associated with the trachea.
therapy was changed to a trimethoprim-potentiated sulphonamide (Sulprim) (Troy ilium, Glendenning, New South Wales, Australia) 30 mg/kg per os q12 hours. The filly was monitored carefully postoperatively for signs of Horner’s syndrome, dysphagia, and development of aspiration pneumonia. 2.4. Gross Pathology and Histopathology The mass was examined after removal. It was heterogeneous and lobulated and well circumscribed except for the two areas of attachment described previously. The cut surface differed in color with some dark red areas, whereas other areas were pale yellow/grey. Some cystic areas with serous fluid were also noted (Fig. 3). Samples were taken from the mass, formalin fixed and sent for further histopathological analysis. On histopathology, some cells were streaming, whereas others had
Fig. 3. Gross appearance of mass after removal.
the appearance of strap cells with abundant trailing eosinophilic cytoplasm and very faint cross-striations. The striations in the cytoplasm of some of the streaming cells were suggestive of striated muscle. Desmin immunohistochemistry was used on samples taken at surgery to refine the diagnosis. The neoplastic cells including streaming, strap forms, those with crossstriations, and other loosely arranged cells were all labeled with desmin, confirming the fact that they were of skeletal muscle origin (Fig. 4). 2.5. Postoperative Care and Outcome After surgery, there was initially a large volume of serosanguinous discharge from the drains, which reduced
Fig. 4. Histological appearance of the cervical mass that was confirmed to be a fetal rhabdomyoma. Notice the spindle to strap cells with eosinophilic cytoplasm and occasional cross-striations. Hematoxylin and eosin stain. Bar ¼ 50 mm. Inset: desmin immunolabeling with cross-striations (arrow). Same magnification.
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after 72 hours. Five days postoperatively, however, increased purulent discharge was noted. A swab of the distal wound was taken for microbiological culture and sensitivity. Culture yielded a mixed growth with no predominant isolate. The Penrose drains were left in situ to allow continuing drainage. The wound was lavaged with several liters 0.5% povidone iodine (Apex Laboratories, Somersby, New South Wales, Australia) in 0.9% sodium chloride (Baxter Healthcare, Old Toongabbie, New South Wales, Australia) solution twice daily. To provide protection, a Lycra hood was applied to cover the incision. Twice daily dressing, changes were carried out using a dry absorbent dressing. The swelling reduced within 72 hours, and the exudate reduced gradually over a period of 12 days. On day 12, the drain and skin staples were removed, antibiotic therapy was discontinued, and the foal was discharged. Three weeks postoperatively, all discharge had stopped (Fig. 5A). Some soft tissue thickening was still evident, which resolved over several months. Because of concerns about possible surgical damage to the vagosympathetic trunk, the foal was monitored carefully for development of dysphagia and pneumonia. Upper airway endoscopy was performed 3 months postoperatively and was within normal limits (grade 1, Lane et al). After 12 months, no recurrence or complications had occurred. The filly was sold at public auction (Fig. 5B) and has successfully raced. 3. Discussion Differential diagnoses for proximal cervical masses in the horse include branchial apparatus anomalies (such as branchial remnant cysts) [8], congenital goiter [9], tumors (teratoma, hemangioma, rhabdomyoma, and hamartoma), retropharyngeal abscesses masses, and parotid salivary gland disease [10]. Branchial remnant cysts typically
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present as a right-sided or dorsal retropharyngeal mass [11]. Congenital vascular tumors and hamartomas are relatively common in foals, but these usually occur as cutaneous nodules [12]. A single case of a subcutaneous fibrous hamartoma has been documented in a foal, which was situated on the lateral aspect of the neck [13]. Other congenital tumors such as teratomas may also occur in the neck region. In man, the neck is the second most common location for teratomas after the sacrum [14]. Ultrasonography is a useful diagnostic aid in differentiation of ventral cervical masses. Branchial remnant cysts have a thick, discrete wall, containing hypoechoic fluid with dependent hyperechoic masses visible [11]. In contrast, soft tissue tumors are likely to be homogenous in appearance. A FNA or biopsy of the mass is necessary for complete diagnosis. A fine needle aspirate is a simple, noninvasive technique commonly used in the diagnosis of head and neck tumors in man [15]. Cytomorphologically, rhabdomyoma tumor cells have eosinophilic finely granular cytoplasm, which can mimic other tumors [16], and misinterpretation of FNA results has been reported in cases of adult rhabdomyoma. Histologically, fetal rhabdomyomas are composed of immature striated muscle at the 6th to 10th week stage of development [17]. Two forms of fetal rhabdomyoma are recognized: myxoid and intermediate types [2]. Histologically, the myxoid type is composed of primitive oval or spindle-shaped cells haphazardly arranged in a myxoid stroma. The intermediate type is more common in adults and generally consists of cells with a greater degree of skeletal muscle differentiation [18,19]. This report found both FNA and tru-cut biopsy results to be inconclusive, highlighting the potential limitations of these procedures, due to small sample size. Immunohistochemical staining for desmin, vimentin, myoglobin, and muscle-specific actin has been used to
Fig. 5. Postoperative follow-up. (A) 21 days post operatively. (B) 12 months post operatively.
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differentiate congenital tumors [18,20]. Desmin is an intermediate filament in a subunit of intermediate filaments in skeletal muscle tissue, smooth muscle tissue, and cardiac muscle tissue. Vimentin, also an intermediate filament protein, is expressed in mesenchymal cells and is used as a nonspecific mesenchymal marker. Fetal rhabdomyoma typically stains for desmin, myoglobin, and muscle-specific actin in mature striated cells. Focal or rare staining for vimentin and smooth muscle actin is seen in primitive cells [19]. In contrast, adult rhabdomyoma is composed of comparatively mature cells that will not stain for vimentin [21]. In man, the recommended treatment for fetal rhabdomyoma is complete surgical excision [18]. Cases of recurrence have been documented in man, attributable to incomplete removal [22]. As results of FNA and tru-cut biopsy were suggestive of a benign mesenchymal tumor, time was given in case of spontaneous regression, which has been reported in cases of some congenital mesenchymal tumors [7]. Complications of surgical excision of masses in the neck region of the horse are divided into three major categories: vascular complications, nerve complications, and wound complications. The recurrent laryngeal nerve can be damaged from direct surgical trauma or secondary to cellulitis and inflammation postoperatively, leading to laryngeal hemiplegia [23]. Laryngeal hemiplegia was seen after branchial cyst resection in 80% of cases, indicating that even with careful dissection around a mass in the proximal cervical region there is a high risk of damage to local neurovascular structures [8]. Other neurovascular structures that may be damaged due to their close proximity include the jugular vein, carotid artery, and vagosympathetic trunk [24]. Transient dysphagia may also be encountered postoperatively [8]. Wound complications in this case occurred as a result of excessive dead space. Dead space results in accumulation of blood and serum, which reduces healing and provides a medium for bacterial proliferation [25]. The top and bottom of wound also varies with head position, and movement of subcutaneous tissues drags skin contaminants in as the horse moves its neck [26]. Bandages are difficult to apply and maintain in this site also due to movement, resulting in contamination of the surgical site. Drains facilitate the debridement phase of healing by providing a means of cellular debris removal. Penrose drains are inexpensive and easy to place and provide good passive drainage [25]. Most commonly they are used as a single exit drain; however, a double exit technique, as used in this report, is advised for neck wounds [26]. With this technique, one end exits the proximal aspect of the wound and the other exits distally. The advantage of this technique in the ventral neck region is that drainage occurs whether the neck is in flexion, neutral, or extended. If drainage persists or increases, a foreign body response should be suspected and the drain removed [25]. Prophylactic antibiotic administration is rarely indicated in the management of open wounds [27]. Postoperative antimicrobials were used in this case as there was concern that wound contamination would develop when using a passive open drainage technique for management of such a large and deep area of dead space.
Antimicrobial concentrations may have been inadequate to inactivate biofilm organisms that could have potentially colonized the drain used in this case, thus potentially selecting for resistant subpopulations of bacteria [28]. With the increasing incidence of antimicrobial resistance, the judicious use of antimicrobials is advocated in veterinary practice [29]. Thus, in retrospect, the authors feel that local wound management alone may have been equally successful in this case. 4. Conclusions Fetal rhabdomyoma should be considered as a differential diagnosis in horses with proximal ventral cervical masses. Immunohistochemistry is required for diagnosis. Prognosis for recovery is excellent after surgical excision, as demonstrated in this case. As with all surgeries in this region, complications are common and care must be taken to avoid damage to neurovascular structures and manage postoperative dead space.
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