Central low-grade osteosarcoma with an unusual localization in the diaphysis of a 12-year old patient

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.

Fibroblastic osteosarcoma in a lion (Panthera leo)

This report describes a case of spontaneous fibroblastic osteosarcoma in the humerus of a lion from a private park in Perugia, Italy. The tumor had an irregular, smooth, brown surface and a generally firm, rubbery consistence with gritty to hard areas interspersed. The mass was poorly vascularized with areas of necrosis at the periphery. The cut surface showed a multilobulated mass that had breached the humeral cortex, with periosteal production of reactive bone. The mass invaded the epiphysis, the synovial membrane, the joint capsule and ligaments. A mild hemorrhagic effusion appeared in the joint space. Clinical signs, gross and histopathologic findings are described in this rare case of a malignant bone tumor.