Due to these striking numbers, the fifth edition of the World Health Organization classification of tumours of the breast (2019) now includes PJS as a genetic tumour syndrome of breast cancer [22], in line with other PVs at high or moderate risk for breast cancer, including established PVs in BRCA1, BRCA2, CDH1, PALB2, ATM, CHEK2, PTEN, and TP53 [23, 24]. The gene discussed is CHEK2; the disease is breast cancer.