Giant cell variant of extraskeletal osteosarcoma

Abstract

The giant cell-rich (GCR) variant of extraskeletal osteosarcoma (ESOS) is a malignant soft-tissue lesion without primary bony involvement. The tumor cells are highly pleomorphic and produce an osteoid matrix, whereas numerous giant cells are present throughout the mass. We describe an unusual case of a 38-year-old female patient who presented with a recurrent gluteal mass. With the help of histomorphological findings and immunohistochemistry (IHC), a final diagnosis of a GCR variant of ESOS arises from the gluteal soft tissue with bony involvement. These malignancies are extremely aggressive and have a high likelihood of recurrence and metastasis; therefore, early detection is crucial for successful management. Standard treatment options include surgery and chemotherapy, and patients should be closely monitored following treatment. With the help of histomorphological findings and IHC, a final diagnosis of a GCR variant of ESOS arises from the gluteal soft tissue with bony involvement. This case is reported to highlight the fact that similar morphology of giant cell osteosarcoma can rarely be seen in soft tissue, and this entity should be kept in mind by the reporting pathologist.