Leiomyosarcoma of the breast: report of a case with fine needle aspiration cytologic, histologic and immunohistochemical features.

BACKGROUND: Leiomyosarcoma of the breast is a rare neoplasm. We present a case of primary leiomyosarcoma of the breast in a middle-aged female in whom fine needle aspiration cytologic features suggested sarcoma. CASE: A 55-year-old female presented with a rapidly growing breast lump of 1 month's duration. On examination, an ulcerating, 12 x 10 cm tumor was seen involving the lower medial and lateral quadrants of the right breast. Fine needle aspiration cytology showed variably sized, dissociated and loosely clustered polygonal, plump and spindle cells with pale blue cytoplasm and vesicular nuclei that were round, oval or irregular. Occasional giant forms and nucleolated and mitotic cells were present. A single cluster of benign ductal cells was seen. The tumor cells did not express immunocytologic reactivity to estrogen receptor protein. A cytologic diagnosis of sarcoma was given with differential diagnoses of metaplastic carcinoma and malignant phyllodes tumor. Histologic study established the diagnosis of leiomyosarcoma. Leiomyosarcoma of the breast shows fine needle aspiration cytologic features of sarcoma, but specific tumor typing may not be possible, especially when the cytologic material is inadequate for ancillary staining required to distinguish leiomyosarcoma from metaplastic carcinoma and malignant phyllodes tumor.