Primary Cutaneous CD4+ Small/Medium Pleomorphic T-Cell Lymphoma

Primary cutaneous CD4+ small/medium pleomorphic T-cell lymphoma (pcSMPTCL) is an extremely rare lymphoma with an overall excellent prognosis. It is a provisional entity in the World Health Organization–European Organization for Research and Treatment of Cancer (WHO/EORTC) guidelines and is considered to have both indolent and aggressive forms. pcSMPTCL typically presents with a persistent, asymptomatic, solitary erythematous nodule or pink plaque on the head, neck, or trunk. Given the generally benign clinical course of this disease, some advocate the use of alternative terms, including T-cell pseudolymphoma, cutaneous nodular proliferation of pleomorphic T lymphocytes of undetermined significance, or clonal T-cell lymphoproliferative disease with indolent behavior [1, 2]. Given the dramatic difference in prognosis between the indolent and aggressive forms, it is possible that this entity, as currently defined, encompasses two distinct diseases. This chapter discusses the clinical presentation, prognosis, treatment, histopathology, immunohistochemistry, molecular characteristics, and differential diagnosis of pcSMPTCL. It closes with a clinical case.