HISTOPATHOLOGY SECTION - CASE REPORT
Year : 2008 | Volume
: 51 | Issue : 1 | Page : 56--57
Extraskeletal osteogenic sarcoma: A rare entity
V Maheshwari, AS Farhan, K Alam Adreena
Department of Pathology, JN Medical College, Aligarh Muslim University, Aligarh, UP, India
Department of Pathology, JN Medical College, Aligarh Muslim University, Aligarh, UP
A 25-year-old female presented with a rapidly increasing painful swelling around right lower thigh and knee for the last 5 months with distant metastasis in the form of lung involvement. X-ray of the part showed only soft tissue swelling without any bony involvement. A diagnosis of extraskeletal osteosarcoma was made which was confirmed by immunohistochemistry.
|How to cite this article:|
Maheshwari V, Farhan A S, Adreena K A. Extraskeletal osteogenic sarcoma: A rare entity.Indian J Pathol Microbiol 2008;51:56-57
|How to cite this URL:|
Maheshwari V, Farhan A S, Adreena K A. Extraskeletal osteogenic sarcoma: A rare entity. Indian J Pathol Microbiol [serial online] 2008 [cited 2021 Jun 20 ];51:56-57
Available from: https://www.ijpmonline.org/text.asp?2008/51/1/56/40398
Soft tissue osteosarcoma is a rare malignancy that accounts for 1% of all soft tissue sarcomas.  Criteria to be fulfilled to designate a soft tissue malignant tumor as extraskeletal osteosarcoma are: the tumor must (1) arise in the soft tissue and should not be attached to bone or periosteum, (2) have a uniform sarcomatous pattern (to exclude the possibility of a mixed malignant mesenchymal tumor), and (3) produce osteoid and/or cartilaginous matrix. Extraskeletal osteosarcomas are usually seen as a complication of long-term radiotherapy given to treat a malignant lesion. So it is more common in chest,  neck,  and oral cavity  and affects patients in the sixth decade of life.  We are presenting a case of this rare tumor in a young female arising in the lower thigh without any predisposing factor or lesion.
A 25-year-old female presented with a huge, rapidly growing, painful swelling around the right lower thigh for 5 months, with restriction of movements at the knee joint. There was history of cough with expectoration for 1 month. There was no history of exposure to carcinogenic agents or radiations. Past history was not contributory.
General examination revealed a thinly built female with mild pallor. Systemic examination was not contributory. Local examination showed a swelling around right knee joint measuring 7 inches in diameter. The overlying skin was shiny, glistening with prominent veins, and raised local temperature. Swelling was tender on palpation, soft to firm in consistency, and margins could be felt separate from the bone. Knee movements were painful and were restricted in terminal degrees of flexion due to mechanical block. There was no neuromuscular deficit distal to the site of tumor.
Hemogram with erythrocyte sedimentation rate, renal function test, liver function test, serum calcium were done, which showed only anemia, with all other investigations within normal limits. X-ray of right lower thigh including knee joint-AP and lateral view revealed only soft tissue swelling, without any involvement of bone. X-ray chest PA view showed multiple round opaque deposits about 0.5-1 cm in diameter.
Fine needle aspiration cytology (FNAC) was done twice, but showed only occasional pleomorphic cells admixed with blood. Hence an incisional biopsy was taken. Histological examination revealed a highly cellular tumor, with anaplastic spindle cell proliferation and presence of immature bone and osteoid matrix [Figure 1]. Tumor giant cells and mitotic figures were also seen. The osteoid was deposited in a coarse trabecular pattern, showing transitions toward mature bone at places. On the basis of the criteria mentioned above, a provisional diagnosis of extraskeletal osteosarcoma was made which was confirmed by positive reactions with alkaline phosphatase on immunochemistry [Figure 2].
As the tumor showed distant metastasis at the time of presentation and the patient was unwilling for disarticulation at the hip joint, the patient was subjected to a combined modality of chemotherapy followed by radiotherapy. The patient died approximately 8 months later from cardiopulmonary failure.
Extraskeletal osteosarcoma is a rare malignancy that accounts for about 1% of all soft tissue sarcomas.  This aggressive high-grade tumor usually affects adults in sixth and seventh decades of life, unlike our case who was in her third decade. Extraskeletal osteosarcoma is usually seen in patients treated by radiotherapy for some other malignant lesion. It is more common in chest,  neck,  and oral cavity.  Lower limbs are rather an unusual site for this rare malignancy; however, few cases have also been reported in liver  , gall bladder,  and mesentery. 
Occasionally, extraskeletal osteosarcoma has been mistaken for myositis ossificans, but the zoning phenomenon, i.e. a fibroblastic center and a zone of ossification at the periphery, helps to exclude the diagnosis of osteosarcoma. This soft tissue neoplasm may mimic other bone forming tumors or tumor-like lesions and therefore pathologists should be aware of this lesion to make a diagnosis of extraskeletal osteosarcoma. 
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