γδ T-cell-rich variants of pityriasis lichenoides and lymphomatoid papulosis: benign cutaneous disorders to be distinguished from aggressive cutaneous γδ T-cell lymphomas.

BACKGROUND: T cells with a γδ phenotype have been associated with aggressive lymphomas. Yet, inflammatory skin disorders and low-grade lymphoproliferative disorders have rarely been described with a predominant γδ T-cell infiltrate.

OBJECTIVES: To review our experience and determine the clinical relevance of the γδ T-cell phenotype in lymphomatoid papulosis (LyP) and pityriasis lichenoides (PL).

METHODS: A retrospective dermatopathology file review looking for LyP and PL characterized by a γδ T-cell phenotype was performed. Clinical manifestations and course, histological features and molecular data were analyzed.

RESULTS: Six of 16 cases of LyP and four of 23 cases diagnosed as PL during a 5-year period (2009-14) were identified. The median follow-up for the whole group was 16 months (range 3-64), showing an indolent clinical course in all cases.

CONCLUSIONS: The detection of a predominantly γδ T-cell phenotype in papular lymphoid-rich infiltrates in the absence of other lesions is not associated with a clinically aggressive course. γδ T-cell-rich variants of LyP and PL may reflect a spectrum of related conditions. This is a single academic centre retrospective chart review of a relatively small sample.