Macroscopic morphology of breast carcinoma: associations with biological subtypes and pathological features.

Background: Morphological features of tumors can reflect the biological behavior of breast carcinoma; however, a consensus macroscopic classification remains elusive. In this study, we aimed to elucidate the relationship between macroscopic morphology and biological behavior of breast carcinoma.

Methods: We evaluated 328 post-operative breast carcinomas, stratifying them by hormone receptor/human epidermal growth factor receptor 2 (HER2) status (luminal-like, luminal-HER2, HER2-positive [non-luminal], triple-negative), and morphological patterns. The tumors comprised infiltrative (n = 101), expansive (n = 93), non-mass (n = 62), mixed (n = 59), and unclassifiable (n = 13). Expansive and non-mass types were sub-classified as acellular, rich vessel, cystic, glossy, comedo, or ductal. Furthermore, we assessed histopathological features, including linear fibrosis, central scar, central cavity, spot necrosis, comedo necrosis, intraductal secretion, and blood spots.

Results: Infiltrative tumors were primarily luminal-like with a central scar (57/101, 56%) and linear fibrosis (98/101, 97%); expansive tumors were frequently triple-negative with spot necrosis (21/93, 23%), and blood spots (33/93, 35%); non-mass tumors were usually HER2-positive (non-luminal) with comedo necrosis (27/62, 44%) and intraductal secretion (42/62, 68%). In histological diagnosis, infiltrative types were commonly invasive breast carcinoma of no special type (54/101, 53%); expansive types included invasive solid papillary carcinoma (iSPC) (21/93, 23%); and non-mass types encompassed ductal carcinoma in situ (DCIS) (28/62, 45%). Rich vessel lesions aligned with iSPC, acellular with squamous cell carcinoma, cystic with encapsulated papillary carcinoma, glossy with mucinous carcinoma, and comedo with high-grade DCIS.

Conclusion: Our findings demonstrated that morphological classification of breast carcinoma correlates with biological features and may aid diagnostic strategies, including imaging and pathological subtype diagnosis.