Clinicopathologic characteristics and prognosis for molecular subtypes in low-grade breast carcinoma: comparison with grade one invasive ductal carcinoma-not otherwise specified

The aim of this study was to investigate the clinicopathologic characteristics and prognosis value for molecular subtypes of low-grade breast carcinoma (LGBC) compared with grade one invasive ductal carcinoma-not otherwise specified (G1-IDC-NOS). A retrospective review of 688 LGBC and 1 037 G1-IDC-NOS patients was classified into four different molecular subtypes based on the IHC-based definitions for ER, PR, and c-erbB-2. In LGBC, lymph node metastasis, the percentage of III/IV TNM stages, the expression of Ki-67 and p53 in luminal A subtype were lower than in other subtypes (P < 0.01). In addition, the variations of Ki-67 and p53 expression were observed in different subtypes of G1-IDC-NOS (P < 0.01). Compared with G1-IDC-NOS, LGBC has higher proportion in the ER positive, PR positive, HER-2 negative, luminal A subtype, Ki-67 negative, and lymph nodes negative group (P < 0.01). Furthermore, the overall survival of luminal A and luminal B is higher than triple-negative and HER-2/neu subtype both in LGBC and G1-IDC-NOS in 262 LGBC and 330 G1-IDC-NOS patients with proper follow-up. The classification of molecular subtype together with clinicopathologic factors can significantly improve the traditional prognosticators in predicting outcome for LGBC and G1-IDC-NOS. And it may contribute to guide the treatment for LGBC and G1-IDC-NOS in the future.