Fine needle aspiration cytologic findings of breast mucinous neoplasms - Differential diagnosis between mucocelelike tumor and mucinous carcinoma

OBJECTIVE: To report the cytologic findings of mucocelelike tumor and mucin ous carcinoma. STUDY DESIGN: All mucinous neoplasms diagnosed by fine needle aspiration an d confirmed by histologic examination were reviewed to detect the cytologic findings helpful for the differentiation. The cytologic findings were corr elated with the histologic findings. RESULTS: Cytologically, mucinous carcinomas were highly cellular and showed many single epithelial cells and variably formed epithelial cell clusters in abundant extracellular mucin. Malignant cells exhibited round, atypical nuclei; granular chromatin; and small nucleoli. Mucocelelike tumor showed l ow cellularity with scanty, monolayered, small sheets of epithelial cells a nd abundant, extracellular mucin. Myoepithelial cells were present within t he epithelial cell sheets. Tumor cells were usually small, with uniform, ro und nuclei; fine chromatin; and absence of nucleoli. CONCLUSION: Cytologic findings of mucocelelike honor and mucinous carcinoma were different in cellularity, shape of cell clusters and nuclear features , although mucocelelike honors having a carcinoma component were similar to mucinous carcinoma. Awareness of the cytologic findings of breast mucinous neoplasms is important to make a specific diagnosis.