Keratoacanthoma

Key Points
Skin condition resembling cancerous conditions
Caused by various factors, most often excessive sun exposure in combination with a minor injury to the area
Initially consists of a small pimple or boil-like lesion with a solid core which grows rapidly

Keratoacanthoma is a false skin cancer, a condition which resembles true skin cancers but is benign. Presentation typically occurs in areas of sun damage which sustain a minor injury. Lesions arise when cells start to build in the hair follicle, eventually forming a mass which grows rapidly. Lesions initially consist of a small pimple or boil-like lesion, which upon attempts to express is found to have a solid core. Rarely, multiple keratoacanthomas may appear in relation to two associated conditions, Ferguson-Smith Familial Keratoacanthoma and Grzybowski Eruptive Keratoacanthomas. Ferguson-Smith Familial Keratoacanthoma consists of large lesions which may ulcerate and are self healing. Grzybowski Eruptive Keratoacanthomas causes the development of thousands of lesions which are very itchy and can result in scarring and deformity.

Keratoacanthoma may be caused by various factors, but it is thought to be linked to sun exposure in combination with a minor injury to the affected area. Other cases may be related to HPV infection. In the case of Ferguson-Smith Familial Keratoacanthoma, men are more likely to develop the condition, but otherwise Keratoacanthoma may affect any person regardless of ethnic, gender or age grouping.

Differential Diagnosis (Other conditions with similar appearance)
Actinic Keratosis
Prurigo nodularis
Cutaneous Horn
Sporotrichosis
Merkel cell carcinoma
Squamous Cell Carcinoma
Metastatic Carcinoma of the Skin
Verrucous carcinoma
Molluscum contagiosum
Muir-Torre syndrome

Diagnosis
Key Points
Diagnosis based on appearance of the lesions
Biopsy must be performed to confirm diagnosis, due to similarities to true skin cancers

Keratoacanthoma is initially diagnosed based on the appearance of the lesion, but a biopsy must be performed to confirm the diagnosis, as extreme similarities exists between it and true skin cancers, such as squamous cell carcinoma.

Treatment
Treatment is recommended to avoid misdiagnosis
Condition may resolve spontaneously
Treatment typically consists of removal or destruction of the lesion

Seeking treatment for keratoacanthoma is highly recommended in light of the danger of misdiagnosis of true skin cancers. Often, treatment is desired for cosmetic reasons, though the lesion will resolve spontaneously if left alone. However, lesions are cosmetically unappealing and the associated pain and tenderness may outweigh the scarring which may result from removal. Several treatments for keratoacanthoma are utilized in its removal, including cryotherapy, curettage and cautery, and surgical excision. Larger lesions may be treated with a course of radiotherapy.