Fine-needle aspiration cytologic features of four special types of breast cancers: mucinous, medullary, apocrine, and papillary.

Recognition of special types of breast cancers by fine-needle aspiration (FNA) cytology may have prognostic implications but some difficulties still exist in the ability of cytopathologists to determine the tumor subtypes. Detailed cytomorphological features were studied in the four special and unusual types of breast cancer cases (8 cases of mucinous, 9 medullary, 9 apocrime, and 11 papillary) and compared between themselves and with those of 32 duct cell carcinomas, not otherwise specified (NOS). Papillary carcinomas were also compared with 10 benign papillary lesions. The significance of the differences was determined using Fishers' Exact Test of Probability. In mucinous carcinoma, the frequency of signet ring cells (62.5%), and background pools of mucin (87.5%) were significantly higher than those of duct cell carcinoma (NOS), medullary carcinoma, apocrine carcinoma, and papillary carcinoma (P = 0.0408 to < 0.0001). In medullary carcinomas, lymphomononuclear cell infiltration (100.0%) was observed in significantly higher number of cases than in papillary, mucinous, and apocrine types (P < 0.0001). Further, moderate to marked nuclear pleomorphism (100.0%) and nuclear irregularity (77.8%) was significantly higher than those of mucinous carcinoma and papillary carcinoma (P = 0.0294 to <0.0003). Abnormal apocrine cells and papillary formation, characterizing all the apocrine carcinomas and papillary carcinomas, respectively, were present in significantly lower number in other variants and in duct cell carcinoma (NOS) (P = 0.0002 to <0.0001). Glycogen vacuoles (63.6%) were observed in a significantly higher number of papillary carcinoma as compared to duct cell carcinoma (NOS), apocrine, and medullary carcinomas (P = 0.0047 to 0.0022). The significant parameters differentiating papillary carcinoma and benign papillary lesions were loose cohesive clusters (P = 0.001) and acinar formation by neoplastic cells (P = 0.0237). Histopathology reports available in 36 cases, confirmed the cytodiagnosis of carcinoma in all 35 cases and the benign lesion in one case. Cytological subtyping was confirmed in 13 of 16 special types of carcinomas and all the 15 duct cell carcinoma (NOS). Thus, special and unusual variants of duct cell carcinomas like mucinous, medullary, apocrine, and papillary have specific cytomorphological features, which differentiate them from one another and from duct cell carcinoma (NOS). However, differentiating features between papillary carcinoma and benign papillary lesions were very few in this study.