Diagnosis: Solitary keratoacanthoma
Our patient had a solitary keratoacanthoma, a unique epidermal tumor that’s characterized by rapid, abundant growth and spontaneous resolution. This tumor goes by many names—molluscum sebaceum, molluscum pseudocarcinomatosum, cutaneous sebaceous neoplasm, and self-healing squamous epithelioma—but keratoacanthoma is the preferred term.1,2
There are several types of keratoacanthoma, but solitary keratoacanthoma remains the most common. It is typically found in light-skinned people in hair-bearing, sun-exposed areas. Peak incidence occurs between the ages of 50 and 69, although the tumors have been reported in patients of all ages. Both sexes are about equally affected, although there is a slight predilection for males. Keratoacanthomas mainly develop on the face (lower lip, cheek, nose, and eyelid), neck, and hands.
The tumors are often considered benign, but they become aggressive in 20% of cases—showing signs of perineural, perivascular, and intravascular invasion and metastases to regional lymph nodes. As a result, some clinicians consider keratoacanthoma to be a pseudomalignancy with self-regressing potential, while others view it as a pseudo-benign tumor progressing into an invasive squamous cell carcinoma (SCC).1,2
The exact etiology of keratoacanthoma is unknown. However, several precipitating factors have been implicated. Primary among them is exposure to ultraviolet light. Other etiological factors include:3-6
- chemical carcinogens (tar, pitch, mineral oil, and cigarette smoking)
- trauma (body peel, carbon dioxide laser resurfacing, megavoltage radiation therapy, and cryosurgery)
- immunosuppression
- surgical scar
- human papilloma virus (HPV).