Subcutaneous, blastic natural killer (NK), NK/T-cell, and other cytotoxic lymphomas of the skin: a morphologic, immunophenotypic, and molecular study of 50 patients.

A new group of subcutaneous, natural killer (NK), NK/T-cell, and other cytotoxic T-cell lymphomas of the skin has been recently described, and some have been included as distinct clinicopathologic entities in the classification of hematologic malignancies recently proposed by the World Health Organization. In the European Organization for Research and Treatment of Cancer classification for cutaneous lymphomas, they would be classified either as CD30- large T-cell lymphoma, small/medium pleomorphic T-cell lymphoma, or subcutaneous T-cell lymphoma. Precise clinicopathologic and prognostic features of all of them have not yet been well characterized. We studied retrospectively 81 biopsies from 50 patients with subcutaneous, blastic natural killer (NK), NK/T-cell, or other non-mycosis fungoides cytotoxic T-cell lymphomas of the skin. Clinical, morphologic, phenotypical, and genetic features and data on Epstein-Barr virus association allowed us to classify our cases according to the following 7 categories: a) subcutaneous "panniculitis-like" T-cell lymphoma (SPTCL): 10 cases (estimated 5-year survival: 80%); b) blastic NK-cell lymphoma: 12 cases (estimated 5-year survival: 0%); c) nasal-type extranodal NK/T-cell lymphoma: 5 patients (estimated 5-year survival: 0%); d) epidermotropic CD8+ T-cell lymphoma: 5 cases (estimated 5-year survival: 0%); e) cutaneous gamma/delta T-cell lymphoma: 8 cases (estimated 5-year survival: 0%); f) cutaneous alpha/beta pleomorphic T-cell lymphoma: 8 cases (estimated 5-year survival: 0%); and g) cutaneous medium/large pleomorphic T-cell lymphoma, not otherwise specified: 2 cases. Our study shows that these cutaneous lymphomas can be classified according to precise diagnostic categories. With the exception of SPTCL, analysis of follow-up data from our patients showed that these groups of lymphomas are characterized by an aggressive course, regardless of the diagnostic category.