Clinical Dermatology

Diagnosis Hallmarks

1. Disttibution - chest, back, and face
2. Square shouldered, sharp margination
3. “Stuck on” appearance

Clinical Presentation

Seborrheic keratoses are flat-topped, brown papules 5 to 20mm in diameter. They are sharply marginated and squareshouldered in cross section. They are always wider than they are tall, and their superficial, exophytic growth pattern gives them a “stuck on” appearance. Early, relatively flat lesions are generally light brown, whereas more advanced, elevated lesions are dark brown or even black. Visible scale is often lacking on early lesions but may be quite apparent on older and larger lesions. Scraping with the edge of a scalpel blade will reveal the presence of scale on lesions of all stages.

Seborrheic keratoses are most commonly found on the chest and back but may also occur on the face and arms. Those that occur around the folds of the neck and near the axillae are often only 2 or 3 mm in diameter and may closely resemble skin tags. Seborrheic keratoses begin to develop in mid adult life and are universally present by age 60. The number of lesions found on patients varies greatly. Some people will have only 1 or 2, whereas others may have as many as 50 to 100.

The diagnosis of seborrheic keratoses is established clinically. They are usually easy to recognize, but sometimes they are confused with actinic keratoses. This problem in differential diagnosis is covered. Confirmation of a clinical diagnosis can easily be obtained via shave biopsy .

Course and Prognosis

The number of seborrheic keratoses present on an individual gradually increases over a period of years. They are permanent lesions; once individualized lesions have fully matured, they remain in place, unchanged, indefinitely. The number of lesions and the age at which they develop seem to be at least partially dependent on genetic factors.

Seborrheic keratoses are benign lesions that have no malignant potential. However, the explosive development of hundreds of lesions may rarely serve 3B a clue to the presence of an internal malignancy. This phenomenon is known as the sign of Leser- Trelat.

Pathogenesis

Seborrheic keratoses represent the proliferation of moderately well differentiated cells from the basal layer area of the epidermis. Unlike the situation with basal cell carcinomas, however, these cells do show evidence of keratinization. Moreover, the cells of a seborrheic keratosis never proliferate in an uncontrolled fashion, nor do they invade the dermis by breaking through the - basement membrane zone.

The reason for the development of these benign tumors is unknown. Their appearance in late adult life suggests that they may be part of the aging process. Genetic factors may also be important, since familial patterns in terms of numbers of lesions and age of onset are often seen. Chronic sunlight exposure seems to play no role in their development.

Therapy

Seborrheic keratoses require no therapy. Nevertheless, patients sometimes wish to have them removed because of their uusightliness and their tendency to catch on clothing. This can be accomplished in a number of ways. Their superficial location allows for easy destruction with cryosurgery or chemocauterants. Alternatively, they can be destroyed with light electrosurgery or can be removed by curettage or shave excision. Because of their pigmented nature, the latter method, which results in a suitable specimen for histologic examination, is preferable for less experienced clinicians. All of these methods result in rather superficial destruction, and while scarring is therefore unlikely to occur, regrowth is sometimes noted. These recurrent lesions can simply be re-treated as necessary.

This entry was posted on Thursday, August 16th, 2007 at 12:17 pm and is filed under Lesions. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.