A rare case report: Malignant transformation of lichen planus

Lichen planus is a chronic inflammatory disease that mainly affects the skin and mucous membranes. Malignant transformation is uncommon and is most frequently reported in oral or genital lesions. We report a rare case of cutaneous lichen planus on the left lower leg that transformed into squamous cell carcinoma with left inguinal lymph node metastasis. 18F-FDG PET/CT demonstrated increased uptake in the primary skin lesion and metastatic lymph nodes, providing important information for staging and treatment planning. This case highlights the potential malignant transformation of long-standing cutaneous lichen planus and the value of PET/CT in evaluating disease extent.