Concomitant Squamous Cell Carcinoma and Mycosis Fungoides Within the Same Lesion: A Case Report and Literature Review.

Concomitant squamous cell carcinoma (SCC) and mycosis fungoides (MF) within the same lesion are exceedingly rare, with only 3 cases previously reported. Cutaneous T-cell lymphoma (CTCL) predisposes patients to malignancies because of immune dysregulation, and treatments such as narrow-band ultraviolet-B phototherapy increase carcinogenic risk. We describe a 78-year-old man with stage IVA1 CTCL who presented with a scaly, painful tumor on his left temple. Biopsy revealed well-differentiated SCC with atypical lymphoid infiltrate consistent with MF, marked by immunohistochemical positivity for CD3, CD5, CD30, and a CD4:CD8 ratio of 50:1. Mohs surgery was performed, and histopathology analysis confirmed the coexistence of SCC and MF, with greater loss of CD7 expression in atypical lymphocytes. Concurrent SCC and MF demonstrate the need for vigilant surveillance for secondary cutaneous malignancies in patients with advanced CTCL. The case presented herein contributes to expand the reported literature and highlights the necessity of individualized management strategies optimized on an individual's Fitzpatrick skin type and unique risk factors.