OBJECTIVETo study the clinicopathologic characteristics of basal-like immunophenotype breast cancer (BLBC).

METHODS458 cases of female infiltrative breast cancer were studied using immunohistochemical staining with an antibody panel of ER, PR, HER2, Ki-67, CK5/6, CK14 and epidermal growth factor receptor (EGFR) and were classified basing on the immunophenotypes. The clinicopathologic characteristics were compared with other immunophenotypes of breast cancer. 228 of 458 cases of breast cancer were followed up.

RESULTS46 cases of BLBC were screened out among the 458 breast cancers. And histological features of BLBC were analysed including the larger diameter of cancer foci (average 3.3 cm), appearance of squeezing phenomenon of neighboring cell borders (58.7%, 27/46), geography-like distribution of necrosis (52.2%, 24/46), central zone fibrosis (30.4%, 14/46) and lymphoplasmacytic infiltration at the margin and stroma (63.0%, 29/46). There were nuclear pleomorphism with numerous mitoses. The cancer cells were closely arranged, forming irregular solid architectures. There was a high expression (> 25%) of Ki-67 (43.5%, 20/46). CK5/6, CK14 and EGFR were positive in 58.7% (27/46), 43.5% (20/46) and 65.2% (30/46) respectively. 3-year survival rate of BLBC was 66.9%, lower than the luminal A breast cancer and similar to HER2 over-expression breast cancer.

CONCLUSIONSThe proportion of BLBC in the group of breast cancers is 10%. BLBC has its distinct histological and cytological features. Currently, it is still necessary to depend on immunophenotyping in making a BLBC diagnosis. BLBC is the one of breast cancer subtypes with the poorest prognosis.