Fine-needle aspiration of breast carcinomas with prominent lymphocytic infiltrate.

Carcinomas of the breast with prominent lymphoplasmacytic background are commonly encountered in cytology. The aim of this study was to assess the prevalence of different types of carcinomas that share this common feature, identify possible distinguishing cytologic features, and evaluate the diagnostic pitfalls in this group of tumors. Eighteen fine-needle aspirations (FNAs) of breast carcinomas with heavy lymphoplasmacytic background were reviewed. Histologic follow-up was reviewed in all cases. Of 18 cases, there were 9 invasive ductal carcinomas (IDC), and 9 medullary carcinomas (6 typical and 3 atypical). FNAs from typical medullary carcinomas (TMC) showed more severe nuclear atypia and macronucleoli than the cases of IDC and atypical medullary carcinomas (AMC). Gland formation was absent in the TMC but was common in IDC and AMC. No cytologic differences were noted between IDC and AMC. Nucleoli were larger in TMC (mean 4, microm) than in AMC (mean, 2 microm) and IDC (mean, 1.5 microm). We conclude that lymphocytes and plasma cells may be seen in different types of breast carcinomas and should not be considered a diagnostic feature of TMC. Features potentially helpful in the cytologic differential diagnosis of a carcinoma with prominent lymphoplasmacytic background are nucleolar size (4 microm in MC, vs. 1.5 and 2 microm in IDC and AMC, respectively) and the degree of nuclear atypia. Lymphocytosis may be part of the carcinoma or may originate from a lymph node involved by metastases. In rare cases, a prominent neutrophilic infiltrate may also be present.