Cytology in Mucinous Breast Carcinoma: Diagnostic Insights and a Rare Bilateral Case

Introduction Cytological evaluation of breast lumps is often conducted as part of the triple test for breast carcinomas and provides a confirmation of the clinical and radiological diagnosis. Mucinous carcinomas of the breast, while a relatively rare entity, are important to recognize due to their favorable prognosis. The present research has been designed to study and highlight the specific cytological features of mucinous carcinoma of the breast as well as present a rare case of cytologically diagnosed bilateral breast mucinous carcinoma. Materials and methods A two-year retrospective analysis of cytologically diagnosed and histopathologically confirmed cases of mucinous carcinoma of the breast was conducted. Relevant clinical and radiological details were noted and included in the study. All slides were assessed for specific features that assist in the final diagnosis of mucinous carcinoma based on cytology alone. Results A total of seven cases of mucinous carcinoma of the breast in a span of two years were identified on cytology. Fine-needle aspiration cytology (FNAC) yielded mucoid material in all cases. Abundant extracellular mucin was observed in all cases. In all cases, there was abundant cellularity. Most of the epithelial cells were seen to be arranged predominantly in clusters. In all cases, cells were uniform and had a moderate amount of cytoplasm and a round nucleus showing mild atypia. Branching, delicate capillary fragments (chicken-wire vascularity) were noted in six (85%) cases. Histopathological correlation was available for all cases, confirming mucinous carcinoma. There was a single case of metachronous bilateral breast mucinous carcinomas, with the right and left breast lesions being palpable five and three years back, respectively, by the patient. Discussion The mean size, age group, and cytological features were consistent with the findings of previous studies. Typically, pure mucinous subtypes show abundant extracellular mucin with floating islands and isolated tumor cells within on histopathology. Mixed mucinous carcinomas often show more solid areas with an invasive ductal carcinoma component. In the present study, there was a single case of bilateral mucinous carcinoma of the breast, making it only the third case to be reported so far. To the best of our knowledge, it is the first case of mucinous carcinoma presenting in bilateral breasts to be reported on FNAC. Conclusion Strict adherence to the above diagnostic cytologic criteria, which includes abundant pools of mucin, tight clusters of epithelial cells exhibiting mild atypia, and branching capillaries, is the key to a confident diagnosis of mucinous carcinoma of the breast on cytology. Though extremely rare, bilateral mucinous carcinoma of the breast does occur and can be reliably diagnosed on cytology.