Uterine pleomorphic leiomyosarcoma with osteoclastic giant cells: Case report with peritoneal washing cytology and cell block study.

Uterine leiomyosarcoma (LMS) with osteoclastic giant cells (OGCs) is extremely rare. However, its morphological appearance and aggressive behavior may have resulted in its being diagnosed as so-called giant cell malignant fibrous histiocytoma (MFH) in the past. Effusions are not uncommon in LMS and may be indicative of an unfavorable prognosis. We report a case with the cytological appearance of a uterine LMS with OGCs metastatic to lower pelvic peritoneum. The pelvic washing specimen consisted of three-dimensional aggregates of atypical cells. The cytohistologic and immunohistochemical study obtained from the cell block and the tumor mass showed overlapping features such as bizarre pleomorphic spindle cells containing numerous evenly dispersed OGCs. The malignant tumor cells showed extensive positivity for desmin, h-caldesmon and multifocal positivity for smooth muscle actin (SMA) whereas OGCs stained with CD68. We stress the usefulness of performing cell block and subsequent immunohistochemistry in order to make an accurate cytohistologic correlation.