keratoacanthoma

Keratoacanthoma is a rapidly growing skin lesion that resembles a squamous cell carcinoma but is generally considered a benign, self-limiting keratinocytic tumor. It most often affects middle-aged to older adults and tends to occur on sun-exposed areas such as the face, ears, and dorsum of the hands. The exact cause is unknown, but ultraviolet exposure, skin injury, and immunosuppression have been linked to its development. Some individuals may develop multiple lesions.

Clinically, a keratoacanthoma presents as a solitary, dome- or cup-shaped nodule, usually 1–2 cm in diameter, with a central keratin-filled crater. The lesion grows rapidly over weeks, stabilizes, and may subsequently involute over months, frequently leaving a scar. Pain is not typical, but nearby skin irritation can occur.

Diagnosis relies on histopathology to distinguish it from squamous cell carcinoma. Typical features include an exophytic, crateriform proliferation of squamous epithelium with a central keratin plug, well-differentiated keratinocytes, and pushing rather than infiltrative margins. Mitotic activity is usually limited, and there is a tendency toward regression in time.

Management generally involves removal of the lesion to confirm diagnosis and ensure complete treatment, especially given diagnostic overlap with carcinoma. Treatments include surgical excision, curettage with cautery, cryotherapy, or electrodesiccation. Mohs micrographic surgery may be chosen for facial lesions or when diagnostic certainty is critical. While spontaneous regression can occur, active treatment is commonly pursued.

Prognosis is usually favorable, with rare metastasis. Recurrence can occur, particularly if removal is incomplete or in cases of multiple lesions.