Acta Derm Venereol 86269 Letters to the Editor Sir, Blastic natural killer-cell lymphoma, also called "agranular CD4+ CD56+ haematodermic neoplasm" is an uncommon type of tumour, which is included in the new World Health Organization (WHO) classification as a malignancy derived from natural killer (NK) cells. It is very aggressive, affecting many organs, and skin involvement is highly characteristic. Several origins have been proposed, but recent studies have shown a relationship with plasmocytoid monocytes.We report here a new case of this rare lymphoma, with skin infiltration as the first manifestation, and with early dissemination to bone marrow and central nervous system (CNS). CASE REPORTA 68-year-old man was referred to our department, with several purple nodules on his back (Fig. 1). These lesions had begun about 3 months earlier and had enlarged rapidly. A punch biopsy revealed a dense infiltrate located on the deep dermis, extending to the subcutis. Tumour infiltration spared the epidermis and subepidermal region with a Grenz zone ( Fig. 2A). The dermal infiltrate was monotonous and composed of mediumsized pleomorphic cells. The nuclei were irregular, with finely dispersed chromatin and several small or medium-sized nucleoli (Fig. 2B). There were no obvious features of angiotropism or angiodestruction.Immunohistochemical studies were performed on paraffinembedded sections of skin lesions. The neoplastic cells reacted positively for CD56 (Fig. 3A), CD4, CD43 and CD68, and negatively for CD3, CD5, CD15, CD20 (Fig. 3B), CD30, CD34, TdT and myeloperoxidase.Polymerase chain reactions showed polyclonal T-cell receptor gamma gene rearrangement. In situ hybridization for Epstein-Barr virus (EBV)-encoded RNAs did not exhibit signals indicating the presence of EBV mRNA within the malignant cells of the infiltrate.A computed tomographic scan of the skull, chest and abdomen, and a bone marrow biopsy specimen revealed no extracutaneous involvement. Analysis of peripheral blood, liver function tests, beta-2-microglobulin, and white and red blood cell counts produced normal results. Specialist examinations did not indicate any involvement of the upper respiratory tract system.During the period of examination (20 days), the skin lesions were fast growing, and anaemia and duplicated serum beta-2-microglobulin levels appeared. A second bone marrow biopsy was made, showing lymphomatous infiltration. Analysis of the cerebrospinal fluid revealed infiltration by lymphoma.A diagnosis of primary cutaneous blastic NK-cell lymphoma with dissemination to bone marrow and CNS was made. High-dose aggressive chemotherapy was established with cyclophosphamide, vincristine, adriamycin, dexamethasone Fig. 1. Violaceous nodules on the back, some with central ulceration.Fig. 2. Biopsy of a tumour. (A) Dense infiltrate in dermis, without epidermotropism, and a Grenz zone below the epidermis (haematoxylineosin ×40). (B) At higher magnification medium-sized cells with irregular nuclei and some mitosis can be observed (haematoxylin-eosin ×100).