Seborrheic keratosis

Seborrheic keratosis
Multiple seborrheic keratoses on the dorsum of a patient with Leser–Trélat sign.
Classification and external resources
Specialty	Dermatology
ICD-10	L82
ICD-9-CM	702.1
OMIM	182000
DiseasesDB	29386
MedlinePlus	000884
eMedicine	derm/397
Patient UK	Seborrheic keratosis
MeSH	D017492

A seborrheic keratosis (also known as "seborrheic verruca" and "senile wart") is a benign skin tumor that originates from keratinocytes. Like liver spots, seborrheic keratoses are seen more often as people 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 across. They can often come in association with other skin conditions, including basal cell carcinoma, as a collision tumor or by means of tumor progression phenomena. At clinical examination the differential diagnosis include, warts (though they have no viral origins) and melanoma (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, and therefore such nomenclature is 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) -- 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 nigra—Commonly found among adult dark-skinned individuals, 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-Trélat

Incidence

Seborrheic keratosis is the most common benign skin tumor with increasing indidence in elderly individuals and no predilection of genre. There is less prevalence in people with darker skin.According to large-cohort studies, 100% of the over-50-year-old patients in their harbored at least one seborrhoeic keratosis. Onset is usually in middle age, although they are a common finding in younger patients—found in 12% of 15-year-olds to 25-year-olds—making the term "senile keratosis" a misnomer.

Etiology

The etiology of seborrheic keratosis is poorly understood. It has been hypeotesized that, since seborrheic keratosis often occurs on sun-exposed areas, ultraviolet light might be involved in their pathogenesis. However, these lesions can also be found on skin that has not been exposed to the sun. Recent insights in the biology of seborrheic keratosis have been provided by the identification of somatic mutations in FGFR3, a growth factor receptor, in the cells composing the lesion.

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.

Diagnosis

Micrograph of a seborrheic keratosis (H&E stain, scanning magnification)

Visual diagnosis is made by the "stuck on" appearance, horny pearls or cysts embedded in the structure. Darkly pigmented lesions can be challenging to distinguish from nodular melanomas. Furthermore, 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.

To date, the gold standard in the diagnosis of seborrheic keratosis is represented by the histolopathologic analysis of a skin biopsy.

Therapy

No treatment of seborrheic keratoses is necessary, except for esthetic reasons. Since a slightly increased risk of localized infection caused by picking at the lesion has been described, if a lesion becomes itchy or irritated by clothing or jewelry, a surgical excision is generally recommended.

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. Also, cryotherapy is a technique based on freezing the seborrheic keratosis growths with liquid nitrogen.

External links

• DermAtlas 185