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Parosteal Osteosarcoma of the Proximal Phalanx of a Finger
CASE REPOSITORY
Parosteal Osteosarcoma of the Proximal Phalanx of a Finger Mohammed Sadiq, MSurg,* Mohammed Ismail, MD,† K. Dhanya, MD,‡ P. Meganath, MSurg*
Osteogenic sarcoma of the hand is very rare and fewer than 50 cases have been reported. There are only 2 previously reported cases of parosteal osteosarcoma involving the phalanges. We report a primary parosteal osteosarcoma involving the proximal phalanx of the right middle finger in a 20-year-old woman, which was managed by ray amputation. There was no evidence of local recurrence or systemic metastasis in the postoperative follow-up period of 2 years. (J Hand Surg Am. 2019;-(-):1.e1-e7. Copyright Ó 2019 by the American Society for Surgery of the Hand. All rights reserved.) Key words Osteosarcoma phalanx, parosteal osteosarcoma.
M
rarely seen in the hand. Fewer than 50 cases of osteosarcoma involving the hand have been reported in the literature. 1 Most are secondary osteosarcomas occurring after prior radiation therapy, pagetoid osteosarcomas, or metastases.1 Among the primary osteosarcomas, the parosteal variant is extremely rare and there are only 6 cases reported to date. Of these, involvement of the phalanx is reported in only 2 cases.2,3 We present 1 such rare case of parosteal osteosarcoma involving the proximal phalanx. ALIGNANT BONE TUMORS ARE
CASE REPORT A 20-year-old woman presented to our hospital with a mass involving the proximal phalanx of the right middle finger of 5 months’ duration. The mass was painless but had rapidly increased in size over the From the *Department of Orthopaedicsa; the †Department of Radiodiagnosis; and the ‡Department of Pathology, ESIC Medical College, Kalaburagi, Karnataka, India. Received for publication May 11, 2019; accepted in revised form August 9, 2019. No benefits in any form have been received or will be received related directly or indirectly to the subject of this article. Corresponding author: Mohammed Sadiq, MSurg, Department of Orthopaedics, ESIC Medical College, SF1, 3rd Floor, Empire Residency, Gubbi Colony, Kalaburagi, Karnataka, India; e-mail: [email protected]. 0363-5023/19/---0001$36.00/0 https://doi.org/10.1016/j.jhsa.2019.08.006
past month. There was no other significant medical history. On physical examination, the mass was nontender and had a bony consistency. The skin overlying the mass was stretched and shiny. There was thinning and discoloration of the skin on the dorsal side, which appeared to be extending along the web spaces (Fig. 1). The finger had developed a swan neck deformity with hyperextension of the proximal interphalangeal (PIP) joint and flexion at the distal interphalangeal (DIP) joint. The patient was incapable of active motion at the PIP and the DIP joints; however, movements at the metacarpophalangeal joint were preserved. Radiographs revealed a lobulated, heavily ossified lesion, circumferentially involving the proximal phalanx. The attachment was broad-based with a radiolucent zone between the lesion and the cortex (Fig. 2). Magnetic resonance imaging showed a circumferential juxtacortical lesion appearing hypointense on T1 and iso- to hyperintense on T2. There was no intramedullary extension and no areas of necrosis (Fig. 3). The extensor tendon was involved; however, the flexor tendons were spared. Computed tomography (CT) showed the presence of a string sign (a streak of radiolucency between the tumor and the parent bone), characteristic of parosteal osteosarcoma.
Ó 2019 ASSH
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Published by Elsevier, Inc. All rights reserved.
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PAROSTEAL OSTEOSARCOMA PHALANX
FIGURE 1: AeC Clinical photographs of the lesion. The mass was globular in shape with apparent extension into the web spaces. The middle finger had developed swan neck deformity because of extensor tendon involvement. Skin involvement was seen on the dorsal side.
FIGURE 2: Plain radiographs of hand (anteroposterior and oblique views) show a lobulated heavily ossified lesion circumferentially involving the proximal phalanx of the middle finger. Minimal periosteal reaction is seen. Radiolucent zone between the lesion and cortex is evident in the anteroposterior view. Tumor is seen extending into the web spaces; however, the PIP and metacarpophalangeal joints are spared.
Complete blood count, erythrocyte sedimentation rate and C-reactive protein revealed no abnormalities. Serum alkaline phosphatase levels (600 IU/L), and J Hand Surg Am.
calcium and phosphorus levels were also normal. A core biopsy was performed from the dorsal side. Histopathology of the lesion revealed well-formed r
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FIGURE 3: A, B Sagittal and coronal CT reconstructions show a circumferential ossified lesion involving the proximal phalanx of the middle finger with a wide base. A string sign is noted. C, D Sagittal T2 and coronal T1 magnetic resonance imaging studies of the lesion demonstrate an iso- to hyperintense lesion on T2 and a hypointense lesion of T1 with subtle cortical irregularity and no intramedullary extension. The extensor tendon is completely involved; however, the flexor tendon is spared.
bony trabeculae and osteoid deposition, rimmed by osteoblasts and spindle-shaped stromal cells, with mild atypia and few mitotic figures, suggestive of well-differentiated osteosarcoma (Fig. 4). A CT scan of the chest and an abdominal ultrasound were performed as a part of tumor staging and showed no evidence of metastasis. The lesion was staged as IB (low-grade, extracompartmental) according to the Enneking surgical staging system of musculoskeletal tumors.4 Surgical planning was made in consultation with the medical and orthopedic oncologist. Considering J Hand Surg Am.
that the tumor was of low grade, it was decided to excise it without preoperative chemotherapy. Under regional anesthesia, a ray amputation of the middle finger was performed, and the transverse metacarpal ligaments were repaired to approximate the index and ring fingers. A wrist orthosis was applied for 2 weeks after surgery. Physiotherapy was started after 2 weeks, and the patient regained full finger movements within 1 month. Grossly, the tumor measured about 5.2 4.6 4 cm (Fig. 5). The histopathological findings were also consistent with well-differentiated r
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FIGURE 4: A Histopathology of the tumor shows well-formed bony trabeculae rimmed by osteoblasts. Hematoxylin-eosin stain; magnification 10. B Spindle-shaped stromal cells with mild atypia and few mitotic figures. Hematoxylin-eosin stain; magnification 40.
FIGURE 5: A Clinical specimen after resection measuring 5.2 4.6 4 cm. B Longitudinal section shows tumor arising from the cortical surface of proximal phalanx with a broad base. The finger extensors are completely involved. The flexor tendons are also surrounded by the tumor.
osteosarcoma. No postoperative chemotherapy was given. The patient was followed every 3 months during the first year and every 6 months thereafter. Abdominal ultrasound was done every 6 months and J Hand Surg Am.
a CT examination of the chest was done after 1 year. There was no evidence of local recurrence or systemic metastasis over a period of 2 years after the surgery (Figs. 6, 7). r
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FIGURE 6: Postoperative radiograph at 6 months shows no evidence of local recurrence. The web space is well approximated.
DISCUSSION Osteosarcoma is rarely seen in the tubular bones of the hand and constitutes about 0.2% of the total cases.1 Previously, only 6 cases of parosteal osteosarcoma of the hand have been reported in the literature.2 Among these, 2 cases have been reported to involve the finger phalanges.3 There are a few nonmalignant conditions of the hand that can be confused with parosteal osteosarcoma. The common differential diagnoses include florid reactive periostitis, bizarre parosteal osteochondromatous proliferation or Nora lesion, myositis ossificans, and aggressive osteoblastoma. The differentiating radiological and histological features are listed in Table 1. In our case, the mass was gradually increasing in size over 5 months and movements at the PIP and DIP joints were restricted. Radiographically, the tumor was found to arise from the surface of the bone as an exuberant growth without any intramedullary extension. Intramedullary extension is seen in about 25% cases of parosteal osteosarcoma.5 Histologically it is a low-grade osteosarcoma with well-formed bony J Hand Surg Am.
FIGURE 7: Clinical photographs show good functional outcome following surgery. The patient is able to perform all fine and gross motor functions using the affected hand. Grip strength was slightly less than the other side.
trabeculae, spindle cell stroma, and minimal cellular atypia.6 Our case had the classic radiographic and microscopic findings of parosteal osteosarcoma. According to Okada et al, osteogenic sarcomas of the hand are less aggressive and have a better response to surgical treatment than at any other site, provided excision is done with a wide margin.7 Ray r
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TABLE 1.
Differential Diagnosis of Slow-Growing Bony Tumors of the Hand
Diagnosis
Most Common Location
Radiological Findings
Histological Findings
Parosteal osteosarcoma
Metacarpal, middle phalanx, proximal phalanx
Large lobulated exophytic mass, usually circumferential involvement String sign—radiolucent line separating the tumor from the cortex
Low-grade tumor Well-formed bony trabeculae and osteoid deposition with or without osteoblastic rimming Stromal cells show mild cellular atypia and few mitoses.
Florid reactive periostitis
Metacarpals and phalanges
Periosteal new bone formation with adjacent soft tissue swelling No cortical break, no intramedullary extension
Irregular bony trabeculae No cellular atypia and necrosis
Bizarre parosteal osteochondromatous proliferation or Nora lesion
Proximal and middle phalanges
Calcified mass adjacent to bones with no cortical flaring No intramedullary extension
Immature bony trabeculae staining deep blue (blue bone) Spindle-shaped chondrocytes No cellular atypia or necrosis
Myositis ossificans
Any site, Previous history of trauma
Calcified soft tissue mass, no bone marrow or cortical abnormalities
Zonal pattern is characteristic: central zone of fibroblasts, intermediate zone of immature osteoid, peripheral zone of mature bone
Aggressive osteoblastoma
Various sites like sacrum, vertebrae, small bones of hands, long bones
Expansile osteolytic lesion arising eccentrically in the medullary cavity with sclerotic rim
Immature interlacing trabecular bone with fibrovascular stroma with prominent capillaries
amputation is required to provide safe margins. The web space gap between the index and the ring fingers should be closed after middle ray amputation in order to improve grip strength and hand appearance. This can be achieved with or without transposition of the index finger. Transposition of the index finger is widely recommended, but it carries the risk of nonunion or malunion, extensor tendon adherence, and a wide first web space with prominence of the second metacarpal stump.8 In our opinion, adequate repair or reconstruction of the dorsal transverse metacarpal ligament can achieve similar functional and cosmetic results as that of transposition. It carries the additional advantage of early finger mobilization. In our case, we only sutured the dorsal ligaments without transposing the finger. We could achieve a good closure of the web space, and full movements were started soon after surgery. There is no role for adjuvant or neoadjuvant chemotherapy in parosteal osteosarcomas because many previous studies have shown no recurrence or metastasis even without chemotherapy.7 Parosteal osteosarcoma is a form of low-grade surface J Hand Surg Am.
osteosarcoma and has a lower risk for metastasis. Chemotherapy is indicated only in high-grade lesions and stage IV disease.9 Primary parosteal osteosarcoma of the finger is a rare tumor with a characteristic radiographic and microscopic appearance. It is important to have a proper histological diagnosis before planning the treatment. In cases of biopsy-proven osteogenic sarcoma, wide excision in the form of ray amputation should be planned. ACKNOWLEDGMENTS The authors thank Shakeebuddin Kashif, MBBS, for coordinating the follow-ups of the patient and Saara Neeha, MD, for advice on the histological findings. REFERENCES 1. Mavrogenis AF, Panagopoulos GN, Angelini A, et al. Tumors of the hand. Eur J Orthop Surg Traumatol. 2017;27(6):747e762. 2. Jones KB, Buckwalter JA, McCarthy EF. Parosteal osteosarcoma of the thumb metacarpal: a case report. Iowa Orthop J. 2006;26: 134e137. 3. Mangini U. Tumors of the skeleton of the hand. Bull Hosp Joint Dis. 1967;28(2):61e103.
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7. Okada K, Wold LE, Beabout JW, Shives TC. Osteosarcoma of the hand. A clinicopathologic study of 12 cases. Cancer. 1993;72(3): 719e725. 8. Gong HS, Shin SI, Baek GH. Creation of a “dorsal transverse intermetacarpal ligament” to prevent scissoring deformity in central ray amputation. J Hand Surg Eur Vol. 2008;33(2):163e165. 9. Carrle D, Bielack SS. Current strategies of chemotherapy in osteosarcoma. Int Orthop. 2006;30(6):445e451.
4. Enneking WF, Spanier SS, Goodman MA. A system for the surgical staging of musculoskeletal sarcoma. 1980. Clin Orthop Relat Res. 2003;415:4e18. 5. Jelinek JS, Murphey MD, Kransdorf MJ, Shmookler BM, Malawer MM, Hur RC. Parosteal osteosarcoma: value of MR imaging and CT in the prediction of histologic grade. Radiology. 1996;201(3):837e842. 6. Hang JF, Chen PC. Parosteal osteosarcoma. Arch Pathol Lab Med. 2014;138(5):694e699.
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Parosteal Osteosarcoma of the Proximal Phalanx of a Finger Mohammed Sadiq, MSurg,* Mohammed Ismail, MD,† K. Dhanya, MD,‡ P. Meganath, MSurg*
Osteogenic sarcoma of the hand is very rare and fewer than 50 cases have been reported. There are only 2 previously reported cases of parosteal osteosarcoma involving the phalanges. We report a primary parosteal osteosarcoma involving the proximal phalanx of the right middle finger in a 20-year-old woman, which was managed by ray amputation. There was no evidence of local recurrence or systemic metastasis in the postoperative follow-up period of 2 years. (J Hand Surg Am. 2019;-(-):1.e1-e7. Copyright Ó 2019 by the American Society for Surgery of the Hand. All rights reserved.) Key words Osteosarcoma phalanx, parosteal osteosarcoma.
M
rarely seen in the hand. Fewer than 50 cases of osteosarcoma involving the hand have been reported in the literature. 1 Most are secondary osteosarcomas occurring after prior radiation therapy, pagetoid osteosarcomas, or metastases.1 Among the primary osteosarcomas, the parosteal variant is extremely rare and there are only 6 cases reported to date. Of these, involvement of the phalanx is reported in only 2 cases.2,3 We present 1 such rare case of parosteal osteosarcoma involving the proximal phalanx. ALIGNANT BONE TUMORS ARE
CASE REPORT A 20-year-old woman presented to our hospital with a mass involving the proximal phalanx of the right middle finger of 5 months’ duration. The mass was painless but had rapidly increased in size over the From the *Department of Orthopaedicsa; the †Department of Radiodiagnosis; and the ‡Department of Pathology, ESIC Medical College, Kalaburagi, Karnataka, India. Received for publication May 11, 2019; accepted in revised form August 9, 2019. No benefits in any form have been received or will be received related directly or indirectly to the subject of this article. Corresponding author: Mohammed Sadiq, MSurg, Department of Orthopaedics, ESIC Medical College, SF1, 3rd Floor, Empire Residency, Gubbi Colony, Kalaburagi, Karnataka, India; e-mail: [email protected]. 0363-5023/19/---0001$36.00/0 https://doi.org/10.1016/j.jhsa.2019.08.006
past month. There was no other significant medical history. On physical examination, the mass was nontender and had a bony consistency. The skin overlying the mass was stretched and shiny. There was thinning and discoloration of the skin on the dorsal side, which appeared to be extending along the web spaces (Fig. 1). The finger had developed a swan neck deformity with hyperextension of the proximal interphalangeal (PIP) joint and flexion at the distal interphalangeal (DIP) joint. The patient was incapable of active motion at the PIP and the DIP joints; however, movements at the metacarpophalangeal joint were preserved. Radiographs revealed a lobulated, heavily ossified lesion, circumferentially involving the proximal phalanx. The attachment was broad-based with a radiolucent zone between the lesion and the cortex (Fig. 2). Magnetic resonance imaging showed a circumferential juxtacortical lesion appearing hypointense on T1 and iso- to hyperintense on T2. There was no intramedullary extension and no areas of necrosis (Fig. 3). The extensor tendon was involved; however, the flexor tendons were spared. Computed tomography (CT) showed the presence of a string sign (a streak of radiolucency between the tumor and the parent bone), characteristic of parosteal osteosarcoma.
Ó 2019 ASSH
r
Published by Elsevier, Inc. All rights reserved.
r
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1.e2
PAROSTEAL OSTEOSARCOMA PHALANX
FIGURE 1: AeC Clinical photographs of the lesion. The mass was globular in shape with apparent extension into the web spaces. The middle finger had developed swan neck deformity because of extensor tendon involvement. Skin involvement was seen on the dorsal side.
FIGURE 2: Plain radiographs of hand (anteroposterior and oblique views) show a lobulated heavily ossified lesion circumferentially involving the proximal phalanx of the middle finger. Minimal periosteal reaction is seen. Radiolucent zone between the lesion and cortex is evident in the anteroposterior view. Tumor is seen extending into the web spaces; however, the PIP and metacarpophalangeal joints are spared.
Complete blood count, erythrocyte sedimentation rate and C-reactive protein revealed no abnormalities. Serum alkaline phosphatase levels (600 IU/L), and J Hand Surg Am.
calcium and phosphorus levels were also normal. A core biopsy was performed from the dorsal side. Histopathology of the lesion revealed well-formed r
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FIGURE 3: A, B Sagittal and coronal CT reconstructions show a circumferential ossified lesion involving the proximal phalanx of the middle finger with a wide base. A string sign is noted. C, D Sagittal T2 and coronal T1 magnetic resonance imaging studies of the lesion demonstrate an iso- to hyperintense lesion on T2 and a hypointense lesion of T1 with subtle cortical irregularity and no intramedullary extension. The extensor tendon is completely involved; however, the flexor tendon is spared.
bony trabeculae and osteoid deposition, rimmed by osteoblasts and spindle-shaped stromal cells, with mild atypia and few mitotic figures, suggestive of well-differentiated osteosarcoma (Fig. 4). A CT scan of the chest and an abdominal ultrasound were performed as a part of tumor staging and showed no evidence of metastasis. The lesion was staged as IB (low-grade, extracompartmental) according to the Enneking surgical staging system of musculoskeletal tumors.4 Surgical planning was made in consultation with the medical and orthopedic oncologist. Considering J Hand Surg Am.
that the tumor was of low grade, it was decided to excise it without preoperative chemotherapy. Under regional anesthesia, a ray amputation of the middle finger was performed, and the transverse metacarpal ligaments were repaired to approximate the index and ring fingers. A wrist orthosis was applied for 2 weeks after surgery. Physiotherapy was started after 2 weeks, and the patient regained full finger movements within 1 month. Grossly, the tumor measured about 5.2 4.6 4 cm (Fig. 5). The histopathological findings were also consistent with well-differentiated r
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PAROSTEAL OSTEOSARCOMA PHALANX
FIGURE 4: A Histopathology of the tumor shows well-formed bony trabeculae rimmed by osteoblasts. Hematoxylin-eosin stain; magnification 10. B Spindle-shaped stromal cells with mild atypia and few mitotic figures. Hematoxylin-eosin stain; magnification 40.
FIGURE 5: A Clinical specimen after resection measuring 5.2 4.6 4 cm. B Longitudinal section shows tumor arising from the cortical surface of proximal phalanx with a broad base. The finger extensors are completely involved. The flexor tendons are also surrounded by the tumor.
osteosarcoma. No postoperative chemotherapy was given. The patient was followed every 3 months during the first year and every 6 months thereafter. Abdominal ultrasound was done every 6 months and J Hand Surg Am.
a CT examination of the chest was done after 1 year. There was no evidence of local recurrence or systemic metastasis over a period of 2 years after the surgery (Figs. 6, 7). r
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FIGURE 6: Postoperative radiograph at 6 months shows no evidence of local recurrence. The web space is well approximated.
DISCUSSION Osteosarcoma is rarely seen in the tubular bones of the hand and constitutes about 0.2% of the total cases.1 Previously, only 6 cases of parosteal osteosarcoma of the hand have been reported in the literature.2 Among these, 2 cases have been reported to involve the finger phalanges.3 There are a few nonmalignant conditions of the hand that can be confused with parosteal osteosarcoma. The common differential diagnoses include florid reactive periostitis, bizarre parosteal osteochondromatous proliferation or Nora lesion, myositis ossificans, and aggressive osteoblastoma. The differentiating radiological and histological features are listed in Table 1. In our case, the mass was gradually increasing in size over 5 months and movements at the PIP and DIP joints were restricted. Radiographically, the tumor was found to arise from the surface of the bone as an exuberant growth without any intramedullary extension. Intramedullary extension is seen in about 25% cases of parosteal osteosarcoma.5 Histologically it is a low-grade osteosarcoma with well-formed bony J Hand Surg Am.
FIGURE 7: Clinical photographs show good functional outcome following surgery. The patient is able to perform all fine and gross motor functions using the affected hand. Grip strength was slightly less than the other side.
trabeculae, spindle cell stroma, and minimal cellular atypia.6 Our case had the classic radiographic and microscopic findings of parosteal osteosarcoma. According to Okada et al, osteogenic sarcomas of the hand are less aggressive and have a better response to surgical treatment than at any other site, provided excision is done with a wide margin.7 Ray r
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PAROSTEAL OSTEOSARCOMA PHALANX
TABLE 1.
Differential Diagnosis of Slow-Growing Bony Tumors of the Hand
Diagnosis
Most Common Location
Radiological Findings
Histological Findings
Parosteal osteosarcoma
Metacarpal, middle phalanx, proximal phalanx
Large lobulated exophytic mass, usually circumferential involvement String sign—radiolucent line separating the tumor from the cortex
Low-grade tumor Well-formed bony trabeculae and osteoid deposition with or without osteoblastic rimming Stromal cells show mild cellular atypia and few mitoses.
Florid reactive periostitis
Metacarpals and phalanges
Periosteal new bone formation with adjacent soft tissue swelling No cortical break, no intramedullary extension
Irregular bony trabeculae No cellular atypia and necrosis
Bizarre parosteal osteochondromatous proliferation or Nora lesion
Proximal and middle phalanges
Calcified mass adjacent to bones with no cortical flaring No intramedullary extension
Immature bony trabeculae staining deep blue (blue bone) Spindle-shaped chondrocytes No cellular atypia or necrosis
Myositis ossificans
Any site, Previous history of trauma
Calcified soft tissue mass, no bone marrow or cortical abnormalities
Zonal pattern is characteristic: central zone of fibroblasts, intermediate zone of immature osteoid, peripheral zone of mature bone
Aggressive osteoblastoma
Various sites like sacrum, vertebrae, small bones of hands, long bones
Expansile osteolytic lesion arising eccentrically in the medullary cavity with sclerotic rim
Immature interlacing trabecular bone with fibrovascular stroma with prominent capillaries
amputation is required to provide safe margins. The web space gap between the index and the ring fingers should be closed after middle ray amputation in order to improve grip strength and hand appearance. This can be achieved with or without transposition of the index finger. Transposition of the index finger is widely recommended, but it carries the risk of nonunion or malunion, extensor tendon adherence, and a wide first web space with prominence of the second metacarpal stump.8 In our opinion, adequate repair or reconstruction of the dorsal transverse metacarpal ligament can achieve similar functional and cosmetic results as that of transposition. It carries the additional advantage of early finger mobilization. In our case, we only sutured the dorsal ligaments without transposing the finger. We could achieve a good closure of the web space, and full movements were started soon after surgery. There is no role for adjuvant or neoadjuvant chemotherapy in parosteal osteosarcomas because many previous studies have shown no recurrence or metastasis even without chemotherapy.7 Parosteal osteosarcoma is a form of low-grade surface J Hand Surg Am.
osteosarcoma and has a lower risk for metastasis. Chemotherapy is indicated only in high-grade lesions and stage IV disease.9 Primary parosteal osteosarcoma of the finger is a rare tumor with a characteristic radiographic and microscopic appearance. It is important to have a proper histological diagnosis before planning the treatment. In cases of biopsy-proven osteogenic sarcoma, wide excision in the form of ray amputation should be planned. ACKNOWLEDGMENTS The authors thank Shakeebuddin Kashif, MBBS, for coordinating the follow-ups of the patient and Saara Neeha, MD, for advice on the histological findings. REFERENCES 1. Mavrogenis AF, Panagopoulos GN, Angelini A, et al. Tumors of the hand. Eur J Orthop Surg Traumatol. 2017;27(6):747e762. 2. Jones KB, Buckwalter JA, McCarthy EF. Parosteal osteosarcoma of the thumb metacarpal: a case report. Iowa Orthop J. 2006;26: 134e137. 3. Mangini U. Tumors of the skeleton of the hand. Bull Hosp Joint Dis. 1967;28(2):61e103.
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7. Okada K, Wold LE, Beabout JW, Shives TC. Osteosarcoma of the hand. A clinicopathologic study of 12 cases. Cancer. 1993;72(3): 719e725. 8. Gong HS, Shin SI, Baek GH. Creation of a “dorsal transverse intermetacarpal ligament” to prevent scissoring deformity in central ray amputation. J Hand Surg Eur Vol. 2008;33(2):163e165. 9. Carrle D, Bielack SS. Current strategies of chemotherapy in osteosarcoma. Int Orthop. 2006;30(6):445e451.
4. Enneking WF, Spanier SS, Goodman MA. A system for the surgical staging of musculoskeletal sarcoma. 1980. Clin Orthop Relat Res. 2003;415:4e18. 5. Jelinek JS, Murphey MD, Kransdorf MJ, Shmookler BM, Malawer MM, Hur RC. Parosteal osteosarcoma: value of MR imaging and CT in the prediction of histologic grade. Radiology. 1996;201(3):837e842. 6. Hang JF, Chen PC. Parosteal osteosarcoma. Arch Pathol Lab Med. 2014;138(5):694e699.
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