Cutaneous Squamous Cell Carcinoma Arising Within a Previously Irradiated Mycosis Fungoides Lesion.

Mycosis fungoides (MF), a form of cutaneous T-cell lymphoma (CTCL), increases the risk of other malignancies. A common and effective treatment for patients with MF is radiotherapy (RT), which itself also increases the risk of malignancies. One such malignancy that may result from both MF and RT is cutaneous squamous cell carcinoma (cSCC). cSCC is the second most common skin cancer in the United States. Prognosis may range from excellent to grim and correlates with the presence of established high-risk features. This case follows a 64-year-old male with a prior diagnosis of MF treated with localized radiation approximately 17 years ago who was found to have a large biopsy-proven moderately differentiated cSCC arising in the scar of an MF radiation site. This patient required general surgery to excise a 10 cm x 20 cm x 2 cm area of skin to have clear deep and peripheral margins. This case underscores the importance of regular skin checks in patients with multiple risk factors for developing cSCC, especially in those with a history of MF, RT, or both to early identify complications before they cause disfigurement or advanced disease.