Can You Identify These Sun-Induced Lesions?

Case 1: Pigmented Lesion

This nickel-sized, spotty, pigmented lesion with sharp borders had been present on a 62-year-old man’s right temple for 1 year. The lesion was asymptomatic. It had not enlarged recently, but the patient noted that it had become more pigmented. He wished to have it removed.

Is this pigmented lesion likely to be malignant?

(Answer and discussion on next page)

ANSWER—Case 1: Actinic keratosis

The lesion was excised in the office under local anesthesia without complications. The pathologic microscopic diagnosis was actinic keratosis with incontinence of pigment and chronic inflammation; there was no evidence of carcinoma. The patient had worked in the Gulf of Mexico on an oil field supply boat most of his life.

Actinic keratoses arise after years of solar damage to the skin, and their numbers increase with age. They are squamous cell carcinomas confined to the epidermis. When they extend more deeply, they are true squamous cell carcinomas. About 60% of squamous cell carcinomas develop from actinic keratoses at a rate of 10.2% over 10 years.¹ Immunosuppression is a risk factor: squamous cell carcinoma occurs 65 times more frequently in transplant patients.¹

Actinic keratoses may be solitary, or several may occur on sun-exposed areas. Inflammation, induration, and oozing herald the development of a true malignancy. Clinical variants include cutaneous horns, pigmented actinic keratoses, and actinic cheilitis. Biopsy, which is necessary for a definitive diagnosis, reveals histologically abnormal epithelial cells confined to the epidermis. Treatment modalities include surgical excision, cryotherapy, and topical medications such as 5-fluorouracil, imiquimod, and diclofenac gel. Advise patients with actinic keratoses to use sunscreen daily. ■

REFERENCE:

1. Habif TP. Clinical Dermatology. 3rd ed. St Louis: Mosby: 1996;736-743.

(Case 2 on next page)

Case 2: Ulcerated Pink Nodule

An 81-year-old man presented with an ulcerated pink nodule on the extensor surface of the right forearm. It had developed over the previous 4 months and had grown rapidly to its present size of 1 cm in diameter. The nodule was asymptomatic.

What are you looking at here?

(Answer and discussion on next page)

ANSWER—Case 2: Keratoacanthoma

The nodule was excised in the office under local anesthesia. Pathologic examination revealed it to be a keratoacanthoma with overlying cutaneous horn; solar elastosis and chronic inflammation were also noted.

Keratoacanthoma is a benign epithelial tumor of unknown etiology that occurs in the elderly. The annual incidence is 104 per 100,000.1 Keratoacanthomas begin as a red papule that rapidly enlarges over a few weeks to months and ulcerates. Most will spontaneously regress over several months.

Because keratoacanthomas most commonly occur on sun-exposed sites, skin cancer is prominent in the differential diagnosis. They grossly resemble nodular basal cell carcinoma; however, they can be differentiated by their more rapid development. Microscopically, keratoacanthoma and squamous cell carcinoma may be difficult to distinguish. Incisional or excisional biopsy is necessary for diagnosis.

Treatment is usually surgical excision. Shave removal with electrodesiccation and curettage may be used for small lesions. Other treatment modalities include topical 5-fluorouracil, imiquimod, and podophyllum resin; intralesional injection of 5-fluorouracil, methotrexate, or interferon alfa-2a; radiotherapy; and oral isotretinoin. ■

REFERENCE:

1. Chuang TY, Reizner GT, Elpern DJ, et al. Keratoacanthoma in Kauai, Hawaii: the first documented incidence in a defined population. Arch Dermatol. 1993;129:317-319.