Similarity in names, overlap in distribution, and concomitant occurrence in older adults sometimes lead to confusion in the identification of seborrheic and actinic keratoses. Appropriate recognition is important, however, because actinic keratoses are premalignant and seborrheic keratoses are totally benign.
Distribution
Actinic keratoses are found only on sun-exposed skin. The face, ears, and Clorsal surface of the hands and arms are most often involved. Lesions may occur on the shoulders, chest, and back in people who have chronically exposed those areas to sunlight.
Seborrheic keratoses, on the other hand, occur predominantly on the the chest, the back, the shoulders, and, only occasionally, the face. In the areas of overlap (the face and the shoulders), consideration should be given to the appearance of the skin adjacent to the lesions. Actinic keratoses do not develop unless there is clinical evidence of chronic sun damage such as hyperpigmentation, mild inflammation, telangiectasia, and atrophy.
Color
Seborrheic keratoses are primarily brown but range from light tan to a dark brown-black. Large, well-established seborrheic keratoses may be covered with a small amount of dirty gray scale. Actinic keratoses are generally white or gray, although some crusted lesions have a yellow hue surface texture. Actinic keratoses demonstrate visible scale and are rough surfaced on palpation. Seborrheic keratoses generally lack visible scale and usually feel smooth on palpation. As mentioned above, however, larger, well-developed seborrheic keratoses may develop a small amount of palpable scale. Most seborrheic keratoses have a somewhat pitted surface; this feature is not seen in actinic keratoses.
Margination
Seborrheic keratoses are very sharply marginated. In cross section they appear square shouldered. Actinic keratoses are less sharply marginated; in fact, sometimes it is difficult to say just exactly where the lesion starts and stops. On occasion, however, dysplastic actinic keratosis will be surmounted by sharply marginated yellow crust.
Supeificiality
Seborrheic keratoses have a stuck on appearance and have often been likened to drops of dirty candle wax on the skin. Actinic keratoses, which are also superficial, look like flecks or discs of scale that are growing from within the skin surface.
Size
Although there is overlap in size, actinic keratoses average 2 to 10 mm in diameter, whereas seborrheic keratoses average 7 to 20 mm in diameter.
Biopsy
Biopsy should be carried out whenever clinical diagnosis is uncertain. Any actinic keratosis with a yellow hue or with a palpable base should be biopsied because of possible transformation to early squamous cell carcinoma. Superficial shave biopsyis all that is necessary for microscopic recognition. Such a procedure heals rapidly without significant scarring and is usually curative also.
Differentiation from Warts
Warts may occur in adults in a distribution similar to actinic and seborrheic keratoses. Generally, warts are skin colored, without any of the pigment changes. Moreover, their rough surface usually has a distinctive digitate or filiform appearance. Finally, these sharply marginated lesions, which average 2 to 7 mm in diameter, tend to be as tall as, or taller than, they are wide. This contrasts to actinic and seborrheic keratoses, which are always wider than they are tall. Nevertheless, in spite of these differences, clinical separation of warts from those actinic keratoses known as cutaneous horns is sometimes impossible without the aid of biopsy.
Tags:actinic keratoses, clinical evidence, Dermatology Diagnosis, mild inflammation seborrheic keratoses
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