MS4A1 and breast cancer: In patients with primary cutaneous melanoma and ovarian cancer CD20+ and CD138+ B-cells, respectively, correlated to decreased overall survival (OS).15,22 In a study by Mahmoud et al., the number of CD20-expressing B-cells in breast tumours was associated with higher tumour grade, hormone receptor negativity and increased breast cancer specific survival.20 In a recent study of ductal carcinoma in situ (DCIS), presence of B-lymphocytes also correlated with hormone receptor negativity and large tumour size.