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

Primary cutaneous gamma delta T-cell lymphoma (PCGD-TCL) is an aggressive lymphoma consisting of clonal proliferation of mature activated gamma delta T-cells of a cytotoxic phenotype. Because primary cutaneous gamma delta T-cell lymphoma is a rare disease, there are few clinicopathological studies. In addition, T-cell receptor (TCR) gamma delta cells are typically immunostained in frozen sections or determined by TCR beta negativity. We retrospectively analyzed 17 primary cutaneous T-cell lymphomas of the gamma delta phenotype (CTCL-gamma delta) in a clinicopathological and molecular study using paraffin-embedded sections. Among 17 patients, 11 had CTCL-gamma delta without subcutaneous panniculitis-like T-cell lymphoma (SPTCL) features and six had CTCL-gamma delta with SPTCL features. Immunophenotypically, some significant differences were found in CD8 and CD56 positivity between our patient series of CTCL-gamma delta patients with SPTCL features and SPTCL-gamma delta patients described in the previous literature. A univariate analysis of 17 CTCL-gamma delta 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-gamma delta 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-gamma delta with SPTCL features and CTCL-gamma delta without SPTCL features (P = 0.0005). Our data suggests that an indolent subgroup may exist in CTCL-gamma delta. Studies on more cases, including those from other countries, are warranted to delineate the clinicopathological features and the significance in these rare lymphomas.