Development of Squamous Cell Carcinoma from Erythroplasia of Queyrat Following Photodynamic Therapy

The document describes a case where a 67-year-old Chinese man with erythroplasia of Queyrat (EQ) developed invasive squamous cell carcinoma (SCC) after undergoing two sessions of photodynamic therapy (PDT) with 5-aminolaevulinic acid. Initially, the patient's erythematous plaque on the glans penis did not respond to cryotherapy. Post-PDT, an ulcerated nodule appeared, leading to a diagnosis of invasive SCC, which was treated with a partial penectomy. Fourteen months after surgery, no recurrence was noted. This case indicates that PDT may not be effective for EQ and could potentially lead to progression to invasive SCC, possibly due to EQ's unique tumor biology. The authors recommend caution when using PDT for EQ, particularly in cases that are resistant to treatment.