Seborrheic keratosis

A seborrheic keratosis (also known as "Seborrheic verruca," and "Senile wart" ) is a noncancerous benign skin growth that originates in keratinocytes. Like liver spots, seborrheic keratoses are seen more often as people age. In fact they are sometimes humorously referred to as the "barnacles of old age". 

They appear in various colors, from light tan to black. They are round or oval, feel flat or slightly elevated (like the scab from a healing wound), and range in size from very small to more than 2.5 cm across. They can resemble warts, though they have no viral origins. They can also resemble melanoma skin cancer, though they are unrelated to melanoma as well. Because only the top layers of the epidermis are involved, seborrheic keratoses are often described as having a "pasted on" appearance. Some dermatologists refer to seborrheic keratoses as "seborrheic warts"; these lesions, however, are usually not associated with HPV, and therefore such nomenclature should be discouraged.

Classification
Seborrheic keratoses may be divided into the following types:


 * Common seborrheic keratosis (Basal cell papilloma, Solid seborrheic keratosis)
 * Reticulated seborrheic keratosis (Adenoid seborrheic keratosis)
 * Stucco keratosis (Digitate seborrheic keratosis, Hyperkeratotic seborrheic keratosis, Serrated seborrheic keratosis, Verrucous seborrheic keratosis)
 * Clonal seborrheic keratosis
 * Irritated seborrheic keratosis (Basosquamous cell acanthoma, Inflamed seborrheic keratosis)
 * Seborrheic keratosis with squamous atypia
 * Melanoacanthoma (Pigmented seborrheic keratosis)
 * Dermatosis papulosa nigra

Also see:
 * The sign of Leser-Trélat

Dermatosis papulosis nigra
Commonly found among adult blacks, presents on the face as small benign papules from a pinpoint to a few millimeters in size.

Stucco keratosis
Often are light brown to off-white. Pinpoint to a few millimeters in size. Often found on the distal tibia, ankle, and foot.

Diagnosis
Visual diagnosis is made by the "stuck on" appearance, horny pearls or cysts embedded in the structure. Darkly pigmented lesions can be hard to distinguish from nodular melanomas. If in doubt, a skin biopsy should be performed. Thin seborrheic keratoses on facial skin can be very difficult to differentiate from lentigo maligna even with dermatoscopy.

Clinically, epidermal nevi are similar to seborrheic keratoses in appearance. Epidermal nevi are usually present at or near birth. Condylomas and warts can clinically resemble seborrheic keratoses, and dermatoscopy can be helpful. On the penis and genital skin, differentiation between condylomas and seborrheic keratoses can be difficult and may require a skin biopsy.

Treatment
When correctly diagnosed, no treatment is necessary. There is a small risk of localized infection caused by picking at the lesion. If a growth becomes excessively itchy or is irritated by clothing or jewelry, it can be removed by cryosurgery.

Small lesions can be treated with light electrocautery. Larger lesions can be treated with electrodesiccation and curettage, shave excision, or cryotherapy. When correctly performed, removal of seborrheic keratoses will not cause much visible scarring except in persons with dark skin tones.

Cause
The cause of seborrheic keratosis is unclear. Because they are common on sun-exposed areas such as the back, arms, face, and neck, ultraviolet light may play a role, as may genetics. A mutation of a gene coding for a growth factor receptor, (FGFR3), has been associated with seborrheic keratosis. . Although a direct cause-effect relationship between physiological stress and tumors in general has not been medically established, stress is medically recognized as a potential factor in the exacerbation of preexisting tumors, including those which are benign. In this view, physiological stress can worsen a preexisting condition such as seborrheic keratosis. Seborheic keratosis can also be one of the many symptoms of gastrointestinal malignancies.

Etymology
The term "seborrheic keratosis" combines the adjective form of seborrhea, keratinocyte (referring to the part of the epidermis that produces keratin), and the suffix -osis, meaning abnormal.