It is our purpose to describe the occurrence on the eyelid of an important benign tumor which is often mistaken for squamous-cell carcinoma and which has not received attention in the ophthalmic literature. This tumor, keratoacanthoma, was established as a clinical entity by MacCormac and Scarff1 in 1936, and since then their observations have been substantiated by others.
The tumor is important because histologically it resembles a low-grade squamous-cell carcinoma and most commonly is diagnosed and treated as a malignant tumor. Judging from the available literature, the dermatologists appear to be the only group of medical practitioners who are generally aware of its existence. Yet its incidence is relatively high, as indicated by reports of as many as 76 cases in one single series.* Among other terms, the tumor has been referred to as molluscum sebaceum, because of a superficial resemblance to molluscum contagiosum, and as molluscum pseudocarcinomatosum; however,