Lethal T- and NK-cell lymphomas mimicking granulomatous panniculitidies: a clinicopathologic study of three cases.

An infiltrate mimicking subcutaneous panniculitis associated with a granulomatous response represents an uncommon histopathologic presentation of lymphoma. We report three cases, comprising one case each of nasal-type extranodal NK/T-cell lymphoma, cutaneous γ/δ T-cell lymphoma and human T-lymphotropic virus-I associated adult T-cell leukemia/lymphoma, which based on initial histopathologic and/or clinical presentation were thought to represent systemic lupus erythematosus, sarcoidosis and psoriasiform dermatitis, respectively. Excisional biopsies of indurated lesions performed at our institute; however, in each case showed an atypical subcutaneous lymphohistiocytic infiltrate associated with a variable number of granulomas. Extensive immunophenotypic characterization, in conjunction with histomorphologic and molecular analysis, established the diagnosis of lymphoma in all instances. All patients had a rapidly progressive clinical course and death was attributable to complications of lymphoma shortly after diagnosis. These cases highlight the importance of using a multimodality diagnostic approach to distinguish lymphomas masquerading as granulomatous panniculitis from inflammatory or reactive disorders associated with such histopathologic patterns.