Analysis of the cytological features supporting the diagnosis of lobular breast cancer. Factors associated with equivocal diagnoses.

Purpose: Lobular carcinoma, the second most frequent type of breast cancer, accounts for 8-14% of all invasive breast cancers and presents a wide spectrum of differences from tumors of ductal origin. Its cytomorphologic features can create diagnostic problems. The purpose of this study was to identify the cytological and immunocytological features that support the diagnosis of lobular breast cancer.

Methods: We retrospectively reviewed and analyzed a series of 46 fine needle aspirates (FNA) of invasive lobular carcinomas confirmed histopathologically. All findings were classified and analyzed in order to identify possible sources of diagnostic failure.

Results: Mammographic features were very subtle in most cases. The detailed cytomorphologic analysis revealed mainly discohesive architecture (95%), little or no nuclear atypia (91.3%), smooth regular nuclear membrane (93.47%) and low mitotic rate (97.8%). Loss of E-Cadherin immunoexpression was found in all cases. Estrogen (ER) and progesterone (PR) receptors were positive in the majority of the cases, whereas C-erbB2 (HER2/neu) was negative.

Conclusion: Discohesive architecture, low grade of nuclear atypia and plasmatoid appearance were the most important features .The correct preoperative diagnosis of lobular carcinoma permits a more specialized therapeutic approach.