ASPIRATION CYTOLOGY OF MALIGNANT INTRADUCTAL MYOEPITHELIOMA OF THE BREAST - A CASE-REPORT

The cytologic features of a fine needle aspiration biopsy of a maligna nt intraductal myoepithelioma of the breast are described. On cytology the tumor cells were shed in cohesive groups consisting of ill-define d polygonal and spindle cells. The latter, which had centrally located , cigar-shaped nuclei, showed a fascicular pattern. Despite cellular m ultilayering, there was a halolike transparency around the nuclei, sug gesting that many cells had clear or pale cytoplasm. Mild nuclear atyp ia was occasionally present. Mitotic figures were also observed. With immunostaining, clustered cells showed a diffuse positive reaction for alpha smooth muscle actin (alpha-SM-actin). The tumor cells prolifera ted intraductally, as in a conventional intraductal carcinoma with a c omedo or solid pattern. Characteristically, zones of clear, polygonal cells were situated at the ductal periphery. Toward the center of each duct, tumor cells were transformed into nonclear cells, and some were further transformed into spindle cells that tended to form fascicles. Immunohistochemically, most of the tumor cells expressed alpha-SM-act in.