Clinicopathological characteristics of mucinous carcinoma of the breast.

Objective: To highlight clinicopathological differences between Pure Mucinous Carcinoma (PMC) and Mixed Mucinous Carcinoma (MMC) of the breast. Study Design: Descriptive Retrospective study. Setting: Private Lab in Faisalabad, Pakistan. Period: January 2017 to December 2022. Methods: FNAC smears diagnosed with Mucinous Carcinoma fulfilling the inclusion and exclusion criteria were carefully examined for features such as cellularity, extracellular mucin (ECM), nuclear pleomorphism, plasmacytoid cells, macrophages, and myxovascular fragments (MVFs). The diagnosis was confirmed by histopathology and were characterized in to PMC and MMC. Immunohistochemistry slides were evaluated according to established protocols. Statistical analysis was performed using SPSS (p < 0.05). Results: The study analyzed 16 FNAC cytological samples with subsequent histopathological confirmation. These cases were derived from a pool of 712 female breast carcinoma cytology cases over a five-year duration. The predominant age group was 40 to 50 years, with the left breast and upper outer quadrant being the most common site. Distinct cytological characteristics, particularly the significant presence of extracellular mucin in PMC, were observed. Tumor grade and lymph node involvement emerged as crucial prognostic factors. MMC exhibited a high Ki-67 index, indicating increased cellular proliferation. Conclusion: Pure mucinous carcinomas (PMCs) are uncommon breast tumors with distinguished cytologic features. It is clinically and genetically distinct from mixed mucinous carcinoma (MMC) and other types of breast cancer. An important prognostic factor is lymph node involvement, and PMCs often have a low proliferation rate and a more favorable long-term prognosis. Therefore, the identification of PMC through FNAC holds significant diagnostic and clinical importance.