History
Seborrheic keratoses usually are asymptomatic, but they can be an annoyance. Lesions can itch and rub or catch on clothing, thereby becoming inflamed.
Lesions often are unattractive and serve as negative psychological connotations—daily reminders of aging. [20, 21]
Patients are sometimes concerned that these enlarging lesions are malignant. Sometimes a person may have many seborrheic keratoses and not notice a dysplastic nevus or a malignant melanoma that develops among the seborrheic keratoses. A significant danger can arise if a person does not detect a malignant melanoma at an early stage.
Although lesions may resolve on occasion, spontaneous resolution does not ordinarily occur.
The sign of Leser-Trélat is the association of multiple eruptive seborrheic keratoses with internal malignancy. Most commonly, the sign is observed with adenocarcinoma, especially of the gastrointestinal tract; however, an eruption of seborrheic keratoses may develop after an inflammatory dermatosis (eg, eczema, [22] severe sunburn). In this latter case, no associated malignancy is expected.
Seborrheic keratoses usually begin with the appearance of one or more sharply defined, light brown, flat macules. The lesions may be sparse or numerous.
As they initially grow, they develop a velvety to finely verrucous surface, followed by an uneven warty surface with multiple plugged follicles and a dull or lackluster appearance.
They typically have an appearance of being stuck on the skin surface.
The color of the lesions can vary from pale brown with pink tones to dark brown or black.
Their natural history includes slow enlargement with increasing thickness and the gradual development of new lesions.
A familial trait exists for the development of multiple seborrheic keratoses in about half of the patients, with an autosomal dominant mode of inheritance.
Seborrheic keratoses can occur on almost any site of the body, with the exception of the palms and soles and mucous membranes. In an Australian study of the site of distribution of 3067 seborrheic keratoses, 54.7% were found on the trunk, 15.2% on the hands, 11.4% on the face and neck, 8.5% on the arms, 2.6% on the upper leg, 6% on the lower leg, and 1.6% on the feet. In this study, the prevalence of seborrheic keratosis was higher on sun-exposed areas compared with nonexposed areas when surface area was taken into account. [23]
Physical Examination
Initially one or more sharply defined, light brown, flat lesions develop with a velvety to finely verrucous surface. They arise on normal skin. Their initial size is usually less than 1 cm, but the lesions can grow to several centimeters or more. With time, the lesions become thicker and have an appearance of being stuck on the skin surface.
Seborrheic keratosis showing lackluster surface and appearance of being stuck on the skin surface.
This is an autosomal dominant form of multiple seborrheic keratoses. This man's daughter is developing a similar distribution and quantity of seborrheic keratoses.
The back of this same patient as in the image above with multiple seborrheic keratoses. His face had a similar number of seborrheic keratoses.
Fully developed seborrheic keratoses often are deeply pigmented and do not reflect light.
Many lesions show keratotic plugging of the surface.
Some lesions are covered by an adherent greasy-appearing scale and are raised above the surface of the skin. Seborrheic keratoses can feel soft and greasy.
The shape is round to oval, and multiple lesions may be aligned in the direction of skin folds.
The smallest lesions are placed around follicular orifices, especially on the trunk.
Most seborrheic keratoses have fewer hairs than the surrounding skin.
Sometimes the lesions can grow large, with individual seborrheic keratoses reaching many centimeters in size.
Epiluminescent surface microscopic examination of seborrheic keratoses reveals globulelike structures. The globule like structures in seborrheic keratoses are due to intraepidermal horn cysts filled with cornified cells containing melanin. They resemble the brown globules observed in melanocytic neoplasms, which are due to nests of melanocytes at the dermoepidermal junction.
Irritation can cause swelling and sometimes bleeding, oozing, and crusting and a deepening of the color due to inflammation.
Seborrheic keratoses may become red-brown in color when they become inflamed.
Variants include the following:
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Dermatosis papulosa nigra: These lesions affect the face, especially the upper cheeks and lateral orbital areas. They are small, pedunculated, and heavily pigmented with a minimal keratotic element. The onset of these lesions generally is earlier than that of ordinary seborrheic keratoses. These lesions appear to be caused by a nevoid developmental defect of the pilosebaceous follicles. Histologically, they show irregular acanthosis and hyperkeratosis.
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Stucco keratosis: Some adults develop large numbers of superficial gray-to-light brown flat keratotic lesions favoring the dorsa of the feet, the ankles, and the dorsa of the hands and forearms. Some investigators think these stucco keratoses are a variant of seborrheic keratosis. Histologically, horn cysts are not observed and a regular spiky papillomatosis with a loose lamellated hyperkeratosis capping the epidermis is prominent.
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Melanoacanthoma: Melanoacanthoma is a deeply pigmented seborrheic keratosis in which an acanthotic proliferation of large dendritic melanocytes is identified. It probably represents a concomitant proliferation or activation of the dendritic melanocytes and epidermal cells.
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Polypoid lesions: A clinical variant of the typical seborrheic keratosis is small polypoid lesions around the neck, under the breast, or in the axillae. They are commonly called skin tags, but different from smooth skin tags, these lesions have a furrowed rough surface. They have a predilection for points of chronic trauma.
Complications
Seborrheic keratoses are an annoyance. Lesions can itch and rub or catch on clothing, thereby becoming inflamed.
Lesions often are unattractive and have negative psychological connotations—daily reminders of aging.
Patients are sometimes concerned that these enlarging lesions are malignant. Sometimes a person that has many seborrheic keratoses may not notice a dysplastic nevus or a malignant melanoma that develops among the seborrheic keratoses. A significant danger can arise if a person fails to detect a malignant melanoma at an early stage.
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Sharply circumscribed elevated seborrheic keratoses.
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Closer view of multiple seborrheic keratoses in an autosomally dominant mode of inheritance.
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Seborrheic keratoses projecting above the level of the epidermis. Cysts represent sections of hyperkeratotic follicles.
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Seborrheic keratosis showing lackluster surface and appearance of being stuck on the skin surface.
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This is an autosomal dominant form of multiple seborrheic keratoses. This man's daughter is developing a similar distribution and quantity of seborrheic keratoses.
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The back of this same patient as in the image above with multiple seborrheic keratoses. His face had a similar number of seborrheic keratoses.
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Acanthotic type of seborrheic keratosis.
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Higher-power view of the cells in an acanthotic seborrheic keratosis.
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Hyperkeratotic type of seborrheic keratosis.
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Reticulated (or adenoid) type of seborrheic keratosis.
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This is a reticulated (or adenoid) seborrheic keratosis with abundant pigment.
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Seborrheic keratosis with inflammation in the dermis.
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This seborrheic keratosis was a pedunculated lesion in an axillary fold. Clinically, it had some resemblance to a skin tag.
