Subcutaneous panniculitis-like T-cell lymphoma: a clinicopathological, immunophenotypic and molecular analysis of six patients.

SummaryBackground Subcutaneous panniculitis-like T-cell lymphoma (SPTCL) is a rare cytotoxic T-cell lymphoma of the skin. In the World Health Organization classification of T-cell and natural killer cell lymphoma it is listed as an example of extranodal lymphoma. In practice, however, it is most likely to present to a dermatologist. Objectives To describe the clinicopathological, immunophenotypic and molecular features of six U.K. patients with SPTCL. Methods The clinical, histological and immunophenotypic features were reviewed. T-cell receptor (TCR) gene analysis was performed on blood and tissue samples using polymerase chain reaction/single-strand conformational polymorphism analysis of the TCR-γ gene using consensus primers. In situ hybridization was performed on lesional skin to detect mRNA for Epstein–Barr virus (EBV). Results All patients presented with subcutaneous nodules, plaques or ulceration, and three had systemic symptoms. All biopsies exhibited an infiltrate of medium to large pleomorphic cells involving the subcutis with characteristic rimming of fat spaces. Five showed areas of necrosis, but only one showed marked cytophagia. In three cases the neoplastic cells did not express TCR-β. One was strongly p53 positive, and the other two were CD56 positive. Both these patients showed epidermal involvement with lichenoid changes histologically, and both developed the haemophagocytic syndrome. The other three cases were TCR-β positive, CD8 positive and CD56 negative. All cases were positive with pan T-cell markers and also for the cytotoxic granule protein T-cell intracellular antigen-1 and granzyme B. All cases were EBV negative both by immunostaining (latent membrane protein-1) and by in situ hybridization (EBV-encoded mRNA). TCR gene analysis revealed a T-cell clone in four of five cases; two of these patients had an identical T-cell clone in the peripheral blood. The median survival was 16 months. However, two of the three TCR-β-negative patients have died, whereas none of the TCR-β-positive patients has died. Conclusions This is the first series of SPTCL patients to be reported in the U.K. and the data support the view that there are two subsets of SPTCL: those derived from γδ T cells which carry a poor prognosis, and are usually CD56 positive, and a more indolent group derived from αβ T cells.