Nonhepatosplenic γδ T-cell Lymphomas Represent a Spectrum of Aggressive Cytotoxic T-cell Lymphomas With a Mainly Extranodal Presentation

Abstract

γδ T cells represent a minor T-cell subset that is mainly distributed in mucosal surfaces. Two distinct lymphomas derived from these cells have been recognized: hepatosplenic γδ T-cell lymphoma (HSTL) and primary cutaneous γδ T-cell lymphoma (PCGD-TCL). However, whether other anatomic sites may also be involved and whether they represent a spectrum of the same disease are not well studied. The lack of T-cell receptor (TCR)β expression has been used to infer a γδ origin when other methods are not available. We studied 35 T-cell tumors suspected to be γδ TCL using monoclonal antibodies reactive with TCR δ or γ in paraffin sections. We were able to confirm γδ chain expression in 22 of 35 cases. We identified 8 PCGD-TCLs, 6 HSTLs, and 8 γδ TCLs without hepatosplenic or cutaneous involvement involving mainly extranodal sites. Two such cases were classified as enteropathy-associated T-cell lymphoma, type II. The other γδ TCL presented in the intestine, lung, tongue, orbit, and lymph node. In addition, we observed 13 cases with mainly extranodal involvement that lacked any TCR expression ("TCR silent"). In all cases, a natural killer cell origin was excluded. In conclusion, the lack of TCRβ expression does not always predict γδ-T-cell derivation, as TCR silent cases may be found. The recognition of γδ TCL presenting in extranodal sites other than skin and liver/spleen expands the clinical spectrum of these tumors. However, non-HSTL γδ TCL do not seem to represent a single entity. The relationship of these tumors with either HSTL or PCGD-TCL requires further study.