Breast Cancer : Basal-like
Molecular Subtypes of Breast Cancer - Basal-like: This heterogenous group of tumors comprises 15% to 20% of all breast cancers and is usually negative for ER, PR, and HER2 (triple negative). They make up 50% to 75% of all ER-negative breast cancers. Not all basal-like tumors are triple-negative and vice versa. The vast majority of basal-like cases are associated with BRCA1 mutations; however, some patients are BRCA1-negative. The patients are relatively younger (more commonly premenopausal) and likely to be of African descent.
Morphologically, these tumors are invasive ductal carcinoma with high histologic grade, brisk mitotic activity (often > 40 mitoses/10 hpf), pushing borders rather than infiltrating borders, dense lymphocytic infiltrate, necrosis, and areas of fibrosis (central scar) (shown in this image). A recognizable in-situ component is usually not seen.