Extranodal NK/T cell lymphoma, nasal type, presenting with primary cutaneous lesion mimicking granulomatous panniculitis: a case report and review of literature.

Background: Cutaneous extranodal NK/T-cell lymphoma, nasal type (NK/T) is relatively rare, associated with aggressive behavior and poor prognosis. Histopathological findings, immunohistochemical study and EBV-encoded RNA (EBER) in situ hybridization are essential for the diagnosis.

Case Report: A 54-year-old Thai man with NK/T of the nasal cavity initially presented with cutaneous NK/T mimicking granulomatous panniculitis. The skin biopsies were performed twice due to the marked necrosis in the first one. The second biopsy revealed small, medium, and large atypical lymphoid cells infiltrating fat lobules with necrotic foci and granulomatous reaction. Within the granulomatous inflammation, the atypical lymphoid cells showing involvement of the blood vessel (angiocentricity) were noted. Immunostaining demonstrated that the atypical lymphoid cells marked with CD3, CD56, and TIA-1, but they did not mark with CD5, CD20, CD15, or CD30. EBER in situ hybridization was positive.

Conclusion: Cutaneous NK/T can produce granulomatous panniculitis. The recognition of atypical lymphoid cells showing angiocentricity together with immunohistochemistry and EBER in situ hybridization are crucial for the correct diagnosis.