To present a case of a rare and challenging disease with an atypical presentation. Methods: Data were collected on eletronical and physical medical records.

A 44-year-old-man was referred to the hematology clinic with a 6-month history of a painlesscutaneous plaque, that progressed to an extensive erythematous tumour lesion with central ulceration and necrosis. During this period, the patient experienced unexplained fever, night sweats and weight loss. His baseline labortatory parameters were normal, including complete blood counts, renal function, calcium and lactate dehydrogenase. A skin biopsy was performed and revealed diffuse infiltration of the skin by medium and large-sized cells with irregularly contoured nuclei, homogenous chromatin, minute nucleolus and scarce cytoplasm, extending from the papillary dermis to the subcutaneous tissue. Immunohistochemical staining showed that the cells expressed CD3, CD56 and CD5 and were negative for CD20, CD4, CD8, CD7 and CD30. In situ hybridization for EBV-encoded small RNA (EBER) showed diffuse positivity, which supported the diagnosis of Extranodal NK/T-cell lymphoma. Positron emission tomography scan (PET/CT) showed an expansive tumour lesion above the right elbow, with SUV of 21. There were no other sites of glycolytic hypermetabolism, including lymph nodes and nasal region. Bone marrow biopsy was not performed. He was treated with 5 cycles of SMILE chemotherapy (methylprednisolone, methotrexate, ifosfamide, L-asparaginase and etoposide) and achieved complete remission. He was then submitted to related allogeneic stem cell transplantation, followed by consolidation radiotherapy at the tumor site and remains alive and in remission of the lymphoma 25 months after the procedure, with mild cutaneous and hepatic chronic graft versus host disease.

Extranodal NK/T-cell lymphoma is characterized by vascular damage, necrosis, cytotoxicphenotype and EBV association, with median patient age of 44-54 years. The most common involved site is the upper aerodigestive tract, specially the nasal area. Extranasal dissemination can occur with the skin involvement being one of the most frequent sites and associated with a worse prognosis. Other unfavourable prognostic factors include advanced-stage disease, high KI-67 proliferation index (40-65%) and high circulating EBV DNA levels. Treatment is based on staging. Radiotherapy is the backbone of treatment of localized disease, often combined with chemotherapy. In advanced disease, multiagent chemotherapy, with asparaginase containing regimes are used, followed by consolidation with allogeneic stem cell transplantation when feasible.

We presented a NK/ T-cell lymphoma case with a rare and exuberant cutaneous presentation that was successfully treated with aggressive chemotherapy followed by stem cell transplantation.