Immunophenotypic shift of CD4 and CD8 antigen expression in primary cutaneous T‐cell lymphomas: a clinicopathologic study of three cases

Primary cutaneous T‐cell lymphomas (CTCL) comprise a heterogeneous group of neoplasms with diverse clinical behavior. Mycosis fungoides (MF) is the most common type of CTCL. Immunophenotypical shift during progression of the disease is a rare event and its significance is unknown. We present three primary CTCL cases that showed an immunophenotypical shift and poor prognosis. Conventional hematoxylin/eosin and immunohistochemical‐stained sections were examined in all the cases. Molecular analysis for rearrangement of the T‐cell receptor (TCR) gene was performed in two cases. One case was classified as MF, while the other two lacked epidermotropism, and were considered primary cutaneous peripheral T‐cell lymphoma (PTCL), NOS. Two cases were CD3+/CD4+ and one case was CD3+/CD8+ at diagnosis. The first two patients suffered many relapses and eventually, new CTCL lesions with a CD3+/CD8+ phenotype were observed. Both cases revealed identical clonal TCR rearrangements on the initial and late lesions, supporting the interpretation of a single clonal proliferation with different phenotypes. The third case progressed with skin recurrences and pulmonary lesions with a predominant CD3+/CD4+/CD8? phenotype. All cases manifested poor prognosis and two patients died of lymphoma. Immunophenotypical shift between CD4 and CD8 in CTCL seems to be a rare phenomenon that may be associated with disease progression.