Blastic natural killer-cell lymphoma of the skin associated with myelodysplastic syndrome or myelogenous leukaemia: a coincidence or more?

We report three patients with blastic natural killer (NK)-cell lymphoma of the skin associated with myelodysplastic syndrome (MDS) (two patients) or subacute myelomonocytic leukaemia (one patient). In two patients MDS was diagnosed before skin lesions; the patient with leukaemia initially presented with skin lesions. Our patients had several clinical features in common, namely multiple skin lesions with a bruise-like appearance, involvement of the oral mucosa, and good general status at presentation but very rapid deterioration in the course of the disease. All patients died of disease 4-14 months after the diagnosis. Histopathologically, there were cutaneous infiltrates of slightly pleomorphic medium-sized cells expressing CD4, CD56, terminal deoxynucleotidyl transferase (focally) and being negative for surface CD3, cytotoxic molecules, B-cell-associated markers and myelomonocytic markers. Erythrocyte extravasation was seen in all patients. T-cell receptor genes were in germline configuration. MDS was classified as refractory cytopenia with multilineage dysplasia and ring sideroblasts and refractory anaemia with transition to refractory anaemia with excess of blasts. We reviewed similar cases reported in the literature showing coexistence of blastic NK-cell lymphoma/leukaemia and MDS or myelogenous leukaemia. We conclude that given an overall limited number of reported cases of blastic NK-cell lymphoma/leukaemia, its association with various myelodysplastic/myeloproliferative disorders seen in a subset of patients ( approximately 15-20%) is more than coincidental and may indicate their common origin.