Melchers RC, Willemze R, Bekkenk MW, et al. - Given the possible association of lymphomatoid papulosis (LyP) with other haematological malignancies (HM), researchers investigated the frequency and prognostic significance of associated HM and non-HM in LyP patients. In this multicentre cohort study, they retrived data of the complete Dutch LyP population from the Dutch Cutaneous Lymphoma Registry between 1985 and 2018. They identified an associated HM, particularly mycosis fungoides and anaplastic large-cell lymphoma (ALCL), in 78/504 (15.5%) patients after a median follow-up of 120 months (range, 6–585). Although associated HM developed at a lower frequency than suggested and the prognosis of most patients with associated HM is excellent, aggressive disease, particularly extracutaneous ALCL, may develop in a small subgroup. In addition, patients with LyP showed a greater risk of developing other malignancies. Clinicians should be informed of these risks, and close monitoring should be undertaken in LyP patients.