JAK2 and myeloproliferative disorder: Of particular note in the multiple cancer case patients is the variant in JAK2 (p.V617F rs77375493), which is very highly somatically mutated in haematopoietic and lymphoid tissues (reported over 40,000 times in COSMIC, ID = COSM12600) and has been reported as a gain of function variant in myeloproliferative disorders [37], as well as acting as a predisposition variant in the germline [38].