γδ lymphomatoid papulosis type D: A histologic mimic of primary cutaneous γδ T-cell lymphoma

Abstract

Gamma-delta T cells represent a small subset of normal human T cells that possess a distinct T-cell receptor (TCR) on their surface. Their exact function has not yet been determined, but these cells are known to play a role in both the adaptive and innate immune system.1 The World Health Organization currently recognizes 2 subtypes of γδ T-cell lymphoma, primary cutaneous γδ T-cell lymphoma and hepatosplenic γδ T-cell lymphoma,2 both of which are rare. Primary cutaneous γδ T-cell lymphoma has an aggressive clinical behavior and poor prognosis, with a meager response to multiagent chemotherapy. However, with the advent of detecting TCR-γδ in paraffin-embedded sections, a few reports have shown examples of indolent γδ T-cell proliferations within the skin, namely in pityriasis lichenoides (PL) and lymphomatoid papulosis (LyP).3, 4, 5 In contrast to primary cutaneous γδ T-cell lymphoma, a retrospective study of TCR-γδ expression in cases of PL and LyP found that such cases have a benign clinical course, with most patients achieving eventual resolution of the lesions and none having lymphoma.4 Here we describe such an example, with a rare case of γδ LyP type D histopathologically mimicking primary cutaneous γδ T-cell lymphoma but having an indolent clinical course. This case further highlights the expanding classification scheme of LyP and aims to bring awareness to this newly described entity to allow distinction from primary cutaneous γδ T-cell lymphoma.