FINE-NEEDLE ASPIRATION (FNA) CYTOLOGY OF ADENOID CYSTIC CARCINOMA ANDADENOMYOEPITHELIOMA OF BREAST - 2 LESIONS OF RICH IN MYOEPITHELIAL CELLS

Adenoid cystic carcinoma and adenomyoepithelioma are relatively rare, but well described, breast lesions. The FNA cytology features in two c ases of mammary adenoid cystic carcinoma and two cases of adenomyoepit helioma are described. In both cases of adenoid cystic carcinoma, aspi rates consisted of tightly cohesive clusters of cells arranged around spheres and interconnecting cylinders of acellular material. The two a spirates of adenomyoepithelioma were composed of large tightly cohesiv e clusters of cells associated with small amounts of stromal material. In all four aspirates a dual population of epithelial and myoepitheli al cells could be identified within cellular aggregates, and numerous bare nuclei were present. Histology revealed the characteristic featur es of adenoid cystic carcinoma and adenomyoepithelioma. Immunohistoche mical staining of histological sections for S-100 protein and alpha-sm ooth muscle actin confirmed the presence of large numbers of myoepithe lial cells within all four lesions, providing indirect evidence that b are nuclei in breast aspirates represent myoepithelial cells. The pres ence of a dual population of epithelial and myoepithelial cells and of numerous bare nuclei within a breast aspirate is generally indicative of a benign lesion. This is not always the case, as adenoid cystic ca rcinoma is a malignant tumour, and adenomyoepithelioma, while generall y exhibiting benign behaviour, is capable of local recurrence and dist ant metastasis.