Fine needle aspiration cytology of apocrine carcinoma of the breast. Review of cases in a three-year period

OBJECTIVE: To describe the fine needle aspiration cytology findings of apocrine carcinoma of breast and correlate them with the histologic appearance. STUDY DESIGN: The author reviewed the fine needle aspiration cytology findings of two cases of pure apocrine carcinoma of the breast in the files of Pamela Youde Nethersole Eastern Hospital during a three-year period, 1998-2000. RESULTS: The cytologic findings in both cases were similar. The smears were of moderate to high cellularity, consisting of predominantly dispersed or loosely cohesive tumor cells in a focally granular background. The carcinoma cells contained abundant, dense to granular cytoplasm; round or oval and sometimes eccentrically located nuclei; a smooth nuclear outline; evenly dispersed chromatin; and solitary macronucleoli. The cell borders were mostly discrete. In contrast to benign apocrine cells, the malignant cells showed nuclear overlapping, more frequent nuclear pleomorphism, increased nuclear/cytoplasmic ratios and occasional mitotic figures. Histologic examination of the excised specimens showed extensive, solid apocrine carcinoma in situ with focal stromal invasion. CONCLUSION: Apocrine carcinoma, a subtype of breast carcinoma characterized mainly by its cytologic features, needs to be distinguished from benign apocrine lesions or other eosinophilic and granular cell tumors of the breast. Recognition of the subtle cytologic differences renders a definitive preoperative diagnosis possible.