Leukaemia cutis as a specific skin involvement in chronic myelomonocytic leukaemia and review of the literature: Acknowledgments.

The skin involvement of myeloid leukaemia is conventionally divided into specific malignant lesions and non-specific benign lesions, and these categories are also applicable in chronic myelomonocytic leukaemia (CMML). According to the 2016 World Health Organization (WHO) classification of tumours of haematopoietic and lymphoid tissues, CMML is defined as a myeloid neoplasm with characteristics of myelodysplastic syndrome (MDS) and myeloproliferative neoplasms (MPNs). As a specific cutaneous sign of extramedullary infiltration, leukaemia cutis (LC) is a rare occurrence in patients with CMML, and only approximately 89 cases have been reported in the literature thus far. The clinical features of LC are varied, and LC in CMML exhibits heterogeneous histopathologic features, with manifestations as cutaneous nodules or papules that are composed of blast cells showing either granulocytic or monocytic differentiation. Skin biopsy and further immunohistochemical examination are essential at the time of diagnosis to evaluate pathological type and determine the clinical course. Generally, once diagnosed as LC in CMML, this unusual skin lesion might be an indicator of transformation to acute myeloid leukaemia (AML) and is associated with a poor prognosis. The main treatment is allogeneic stem cell transplantation (ASCT). Therefore, early diagnosis and accurate identification have important therapeutic and prognostic significance in CMML patients with skin infiltration.