CD56-positive cutaneous lymphoma: a poorly recognized entity in the spectrum of primary cutaneous disease.

CD56-positive (CD56+) lymphomas, characterized by the expression of the neural cell adhesion molecule on pathological lymphocytes, share a frequent extranodal involvement and a generally aggressive course. Five CD3- CD56+ lymphoma patients presenting with nodular lesions were identified among 180 immunophenotyped cutaneous lymphomas. All the patients were men, with ages ranging from 55 to 78 years. After staging, two patients were diagnosed as having primary cutaneous lymphomas; the remaining three had the secondary cutaneous type. The clinical course was aggressive and four patients died within 8 months from diagnosis. The remaining patient is still alive after a 17-month follow-up. The histological diagnosis was immunoblastic lymphoma in two patients, and medium and large cell pleomorphic lymphoma in three. The angiocentric infiltrate was located mainly in the dermis; azurophilic granules were present in three of the five patients. Immunogenotypic analyses suggested the natural killer cell origin of these neoplasias: all cases exhibited a CD56+ CD3- CD5- T-cell receptor (TCR) silent phenotype, and Southern blot analysis showed a germline configuration of the TCR beta-chain gene.