Low-Grade Central Osteosarcoma: Report of Two Unusual Morphologic Variants.

Low-grade central osteosarcoma (LGCO) is a rare subtype of osteosarcoma, constituting < 2% of all osteosarcomas. If not treated appropriately, the tumor can recur with higher-grade disease. We report two cases of low-grade central osteosarcoma with unusual morphologic features and belonging to different age groups. Both presented with pain and swelling in the lower end of femur. Radiologically, both the lesions revealed a large mass with irregular borders and soft tissue invasion. One patient underwent above-knee amputation and wide local excision of tumor was done in the other patient. Histologically, both the tumors showed spindle cell proliferation displaying mild atypia. In synopsis with radiology, diagnosis of low-grade central osteosarcoma was made in both cases. These cases highlight the varied morphological spectrum of low-grade central osteosarcoma and underscore the diagnostic difficulties faced. Recognition of the variants of low-grade central osteosarcoma is based on aggressive radiological appearance and on adequate tumor sampling for histologic examination.