Penis keratoacanthoma transforming into squamous cell carcinoma: a rare case.

Keratoacanthoma is variously regarded as a benign epithelial tumor, characterized by a rapid-growing and solitary flesh-colored nodule with a central keratin plug on the sun-exposed skin. Under certain circumstances, it can transform into squamous cell carcinoma. In this paper, we present a case of a 50-year-old man with a 2.5 × 3 × 2.2 cm mass on his penis stub-end. The patient was treat with a partial penectomy after further expert discussions and histopathology the lesion demonstrated penis keratoacanthoma. He received a partial penectomy again and the pathological result revealed squamous cell carcinoma this time. This case indicates that undergoing a partial penectomy on initial diagnosis of a penile tumor secondary to penile keratoacanthoma should be considered because of its high malignant potency. To our best knowledge, this is the first study to describe the malignant conversion of penis keratoacanthoma.