Keratosis Seborrheic

# Overview
A seborrheic keratosis (also known as "seborrheic verruca," and "senile wart":767:637) 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".
The lesions 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 centimetres (0.9842519675 in) across.  They can resemble warts, though they have no viral origins. They can also resemble melanoma skin cancer, though they are unrelated to melanoma.  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,Template:Citation needed (lead) and therefore such nomenclature is discouraged.

# Epidemiology
Presence and frequency increase with age: almost all elderly patients have some. An Australian study found 100% of the over-50-year-olds in their sample had at least one seborrhoeic keratosis (median number of 23 keratoses in the 51-75 year range, and 69 keratoses in the over-75-year-olds).
Onset is usually in middle age, although they are a common finding in younger patientsfound in 12% of 15-year-olds to 25-year-oldsmaking the term "senile keratosis" a misnomer.
No difference in prevalence exists between the sexes. There is less prevalence in people with darker skin.

# Classification
Seborrheic keratoses may be divided into the following types::769770
- 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) -- Often are light brown to off-white.  Pinpoint to a few millimeters in size.  Often found on the distal tibia, ankle, and foot.
- Clonal seborrheic keratosis
- Irritated seborrheic keratosis (basosquamous cell acanthoma, inflamed seborrheic keratosis)
- Seborrheic keratosis with squamous atypia
- Melanoacanthoma (pigmented seborrheic keratosis)
- Dermatosis papulosa nigraCommonly found among adult African Americans, presents on the face as small benign papules from a pinpoint to a few millimeters in size.
- Inverted follicular keratosis
Also see:
- The sign of Leser-Trelat

# 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, condylomas and seborrheic keratoses can be difficult to differentiate, even on biopsy.

## Physical examination

### Skin
- Keratosis seborrheic. Adapted from Dermatology Atlas.
- Keratosis seborrheic. Adapted from Dermatology Atlas.
- Keratosis seborrheic. Adapted from Dermatology Atlas.
- Keratosis seborrheic. Adapted from Dermatology Atlas.
- Keratosis seborrheic. Adapted from Dermatology Atlas.
- Keratosis seborrheic. Adapted from Dermatology Atlas.
- Keratosis seborrheic. Adapted from Dermatology Atlas.
- Keratosis seborrheic. Adapted from Dermatology Atlas.
- Keratosis seborrheic. Adapted from Dermatology Atlas.
- Keratosis seborrheic. Adapted from Dermatology Atlas.
- Keratosis seborrheic. Adapted from Dermatology Atlas.
- Keratosis seborrheic. Adapted from Dermatology Atlas.

# Treatment
No treatment of seborrheic keratoses 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.
Small lesions can be treated with light electrocautery.  Larger lesions can be treated with electrodesiccation and curettage, shave excision, or cryosurgery.  When correctly performed, removal of seborrheic keratoses will not cause much visible scarring except in persons with dark skin tones.

# Cause
The causes of seborrheic keratosis are unclear. Because seborrheic keratoses are common on sun exposed areas such as the back, arms, face, and neck, ultraviolet light may play a role, as may genetics. However, they are also found on skin that has not been exposed to the sun. A mutation of a gene coding for a growth factor receptor, (FGFR3), has been associated with seborrheic keratosis.

# 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.