Abstract

A 87-year-old man with two different tumors in their appearance on his left cheek was reported. One was a dome-shaped pink tumor which was filled with keratin in the center. The other one was an irregular-surfaced brown tumor. Those were contact intimately with each other. Histopathologically, the former was a keratoacanthoma-like squamous cell carcinoma (SCC) and the latter was a malignant trichilemmoma (MT) in situ. Detail observations of the lateral margins of the tumors and the transition part between the tumors gave the evidences which pre-existent actinic keratosis (AK) was responsible for the both tumors. It was figured out that AK caused not only SCC but also MT.