Primary Cutaneous T-cell Lymphoma With Coexpression of T-Cell Receptors αβ and γδ.

T lymphocytes belong to 2 distinct sublineages that express either αβ or γδ T-cell receptor (TCR) complex. Although malignancy is a great instigator of lineage infidelity, as exemplified by aberrant expression of numerous lineage markers in lymphoma cells, malignant T cells rarely coexpress αβ and γδ TCR complexes. Similarly, only rare cases of CD4/CD8 double-positive primary cutaneous T-cell lymphoma have been reported. In this report, we describe a remarkable case of primary cutaneous T-cell lymphoma coexpressing αβ and γδ TCR complexes, strong diffuse CD8, and a very restricted coexpression of CD4 and CD8. A 66-year-old man was referred to our center for treatment of a persistent eczematoid eruption of 6 years of duration. An initial biopsy demonstrated not only marked spongiosis, but also an epidermotropic population of CD4 small mature T cells with partial expression of CD8. The process remained indolent for another year, followed by an abrupt progression with development of plaques and tumors. Repeat biopsies of these lesions demonstrated a superimposed population of large anaplastic T cells extensively involving the dermis and epidermis. The large cells showed a strong uniform expression of CD3, CD8, CD45RA, CD5, granzyme, TIA1, perforin, TCR-β, and TCR-γ and a weaker but unambiguous expression of CD4, CD25, CD2, and CD56. TCR gene rearrangement studies showed clonal rearrangements for TCR-β and TCR-γ with identical peaks to those seen in the biopsy from a year earlier. The patient developed lymphadenopathy, with a biopsy showing nodal involvement by a morphologically and phenotypically identical neoplastic T-cell population. The disease showed partial response to systemic chemotherapy with development of new plaques, but these new lesions have regressed with radiation therapy.