Characteristics and prognosis of 17 special histologic subtypes of invasive breast cancers according to World Health Organization classification: comparative analysis to invasive carcinoma of no special type

Background Breast cancer is a heterogeneous disease with various histopathologic subtypes. Except for invasive carcinoma of no special type (NST), other subtypes are rare with limited data. The purpose of this study was to analyze the characteristics and prognosis of special histopathologic subtypes of breast cancer compared to NST. Methods A total of 136,140 patients were analyzed using the Korean Breast Cancer Society Registry database between January 1996 and March 2019. The clinicopathologic features and survival outcomes of special type breast carcinoma were compared with those of NST. Results The prevalence of special subtypes other than NST was 13.7% ( n = 18,633). Compared to NST, patients with lobular, medullary, metaplastic, and micropapillary carcinoma had larger tumors ( p