Small Cell Extraskeletal Osteosarcoma: A Rare Case Report
A-60-years-old woman presented with large, slowly enlarging and painful lesion in left thigh since last 18 months. She gave a history of trauma at the onset. On examination the lesion was firm, non mobile, fixed to skin and underlying structures on lateral aspect of thigh. MRI showed a variegated mixed intensity lesion in antero-medial aspect of left thigh arborizing left adductor, obturator, pectineus, vasti and fringe of sartorius and ilio-psoas musculature and enclosing neuro-vascular bundles with cystic degeneration, necrosis and associated solid density lesional matrix and discrete calcific foci (). Patient was referred for fine needle aspiration cytology (FNAC) of lesion and smears showed diffuse sheets of small round cells with mild pleomorphism, high nuclear cytoplasmic ratio (N:C ratio) and dark fine granular chromatin without classical rosseting pattern with few foamy histiocytes and scant osteoid (, ). A diagnosis of small round cell tumor with possibilities of ESOS and PNET was given. The lesion was then excised and sent for histopathological examination.\nGross examination of specimen showed an irregular, infiltrating firm, grey white lobulated growth measuring 17×13.5×8.7 cm invading skeletal muscle fibers. Focal gritty areas were observed ().\nMicroscopy showed nodules and islands of tumor with focal malignant lace like as well trabecular mineralized and non-mineralized osteoid formation without any cartilage or zoning pattern (). Trichrome stain highlighted neoplastic osteoid (). Extensive areas of necrosis were also observed. Tumor cells were small, round with inconspicuous cytoplasm, dense coarse chromatin with minimal pleomorphism with 1-2 mitosis/hpf and small round cells show PAS positivity (). Tumor was invading attached skeletal muscle fibers and fat however the resected skin, soft tissue margins and separately sent lymph nodes were free of tumor. S100 (), LCA, smooth muscle actin, chromogranin, desmin, pancytokeratin and EMA were negative. Patient was monitored for 6 months and was uneventful thereafter lost for further follow up.