Soft-tissue osteosarcoma with prominent aneurysmatic bone cyst-like features: a case report.

We describe the cytological features of a soft-tissue high-grade spindle and pleomorphic sarcoma. The smears showed hypercellularity composed of pleomorphic round and elongated cells, and a striking population of multinucleated osteoclast-type giant cells. Microscopically the tumor showed multiple patterns such as highly cellular pleomorphic, less cellular, and hyalinized areas with neoplastic cartilage and osteoid, and areas with hemorrhage and multicystic appearance with numerous osteoclastic giant cells, resembling aneurysmal bone cysts. Immunohistochemical studies showed positivity for vimentin, while chondroid tissue was positive for S-100, and osteoclastic giant cells stained positively for CD68. Due to the varied microscopic patterns, the differential diagnosis included many tumors containing osteoclastic giant cells and osteochondroid tissue.