Within a cohort of 1,915 consecutive patients with myeloproliferative neoplasm followed for a median time of 5.2 years (range 0–33.3), we investigated the occurrence of lymphoid neoplasm with the aim of defining this risk and to investigate the role of genetic predisposing factors. We identified 22 patients with myeloproliferative neoplasm who developed lymphoid neoplasm over their lifetime. We found that the risk of developing lymphoid neoplasm was 2.79-fold higher (95% CI, 1.80–4.33; P