Gamma-Delta and CD20 Mycosis Fungoides: Two Cases Uncovered by Broad-Spectrum Immunostaining

Mycosis fungoides (MF) expresses T-cell markers and the alpha-beta T-cell receptor (TCR) complex. Here, we describe a case of MF with dual expression of TCR delta and TCR beta and a case of MF expressing the B-cell marker CD20. Both anomalies were detected after we instituted a broad-spectrum immunostaining panel for cutaneous T-cell lymphomas. These findings suggest anomalous immunophenotypes may be more common in MF than previously appreciated. Histopathologists should be aware of unexpected malleability in the immunophenotype of MF to avoid confusion with other subtypes of cutaneous lymphoma. Further research into the prevalence and significance of CD20 and TCR-delta expression in MF is encouraged.