Keratoacanthoma: Histopathologic Criteria for Diagnosis

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KERATOACANTHOMAS appear as firm, white, keratotic nodules on the skin of the face or of the dorsum of the hand. They are characterized by rapid growth to maximum size and benign biologic behavior. On microscopic examination, under high-power magnification they possess some of the features of low-grade, superficial squamous cell carcinoma, and under low-power magnification they resemble to a degree molluscum contagiosum.

The disparity between the architecture and the behavior of keratoacanthomas has attracted the worldwide attention of dermatopathologists who have proposed numerous descriptive names for the lesions. For the most part their nomenclature reflects the superficial, benign nature of this group of tumors. Freudenthal1 first suggested “keratoacanthoma”; MacCormac and Scarff2 in their report of ten cases suggested “molluscum sebaceum”; and Poth3 suggested “tumor-like keratoses.” A recent LANCET editorial4 noted the 76 cases described by Beare5 and suggested the name “molluscum pseudocarcinomatosum.”

In an effort to establish definitive histopathologic criteria as a basis for the diagnosis of keratoacanthoma, we undertook a comparative histopathologic study of the biopsy specimens from the 14 cases of the lesion seen here since 1948.

Materials and Methods

Of approximately 42,000 surgical specimens screened for the presence of low-grade squamous-cell epitheliomata, 377 qualified; however, only 14 of the latter were lesions with both the macroscopic and the microscopic findings consistent with a diagnosis of keratoacanthoma.

Clinical Features

The diagnosis of keratoacanthoma was confirmed in ten men and four women. In seven patients the lesions occurred on the hand or wrist, and in the remaining seven they . . .



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