Verrucous cell carcinoma arising from an underlying giant keratoacanthoma.

Keratoacanthoma is a well-known, fast-growing, benign squamous epithelial neoplasm that usually presents as a solitary, dome-shaped, pink or flesh-colored nodule developing a central keratin-filled crater. Few authors consider it to be a benign cutaneous tumor whereas others suggest that it should be regarded as a low-grade variant of cutaneous squamous cell carcinoma (SCC). A 21-year-old female presented with a firm, nontender, well-defined plaque with irregular margins measuring about 8 × 4 cm over the dorsal aspect of the right foot along with an exuberant growth from the plaque measuring 4 × 5cm. There was no lymphadenopathy. Systemic examination was within normal limits. Routine investigations, including complete blood counts, liver and renal function tests, urinalysis, chest radiographs, and abdominal ultrasonography, were normal. Histopathological examination of a skin biopsy from the plaque showed features suggestive of keratoacanthoma, whereas exuberant growth overlying the plaque showed features of verrucous carcinoma (a variant of SCC). Thus, it represents a case of SCC arising from a giant keratoacanthoma.