単一病変における光線角化症と線維肉腫の衝突による診断上の落とし穴：症例報告

Dermatofibrosarcoma protuberans (DFSP) is a rare locally aggressive cutaneous sarcoma, whereas actinic keratosis (AK) is a common premalignant epidermal lesion. The coexistence of these two entities within a single facial lesion is extremely rare and may complicate diagnosis, particularly when an initial biopsy captures only the epidermal component. We present the case of an 80-year-old man with a persistent facial lesion initially diagnosed as AK on punch biopsy. Owing to the atypical clinical features, a repeat deep biopsy revealed the coexistence of DFSP and bowenoid AK. Immunohistochemistry confirmed the presence of DFSP with strong CD34 expression. The lesion was excised using Mohs micrographic surgery to achieve clear margins. This case highlights the importance of clinicopathological correlation and repeat biopsy for the accurate diagnosis of complex skin lesions. Surgical excision with sufficient margins is the key for optimal management.