Clinicopathological analysis of 17 primary cutaneous T-cell lymphoma of the γδ phenotype from Japan

Primary cutaneous γδ T-cell lymphoma (PCGD-TCL) is an aggressive lymphoma consisting of clonal proliferation of mature activated γδ T-cells of a cytotoxic phenotype. Because primary cutaneous γδ T-cell lymphoma is a rare disease, there are few clinicopathological studies. In addition, T-cell receptor (TCR) γδ cells are typically immunostained in frozen sections or determined by TCRβ negativity. We retrospectively analyzed 17 primary cutaneous T-cell lymphomas of the γδ phenotype (CTCL-γδ) in a clinicopathological and molecular study using paraffin-embedded sections. Among 17 patients, 11 had CTCL-γδ without subcutaneous panniculitis-like T-cell lymphoma (SPTCL) features and six had CTCL-γδ with SPTCL features. Immunophenotypically, some significant differences were found in CD8 and CD56 positivity between our patient series of CTCL-γδ patients with SPTCL features and SPTCL-γδ patients described in the previous literature. A univariate analysis of 17 CTCL-γδ patients showed that being more than 60 years old, presence of visceral organ involvement, and small-to-medium cell size were poor prognostic factors. In addition, the 5-year overall survival rate was 42.4% for the CTCL-γδ patients without SPTCL features and 80.0% for those with SPTCL features. Consequently, there was a strikingly significant difference in overall survival among SPTCL, CTCL-γδ with SPTCL features and CTCL-γδ without SPTCL features (P = 0.0005). Our data suggests that an indolent subgroup may exist in CTCL-γδ. Studies on more cases, including those from other countries, are warranted to delineate the clinicopathological features and the significance in these rare lymphomas.