Seborrhoeic warts

What are seborrhoeic warts?

Seborrhoeic warts are also known as seborrhoeic keratoses or basal cell papillomas. In the past they were also called senile warts.

They usually look like greasy or crusty spots which seem to be stuck on to the skin. The colour varies but usually they are darkish brown or black. Seborrhoeic warts can occur almost anywhere on the body, but particularly on the face, chest, scalp, back and groin.

Dermatosis papulosa nigra are multiple, small, 1–5 mm diameter, smooth, firm, black or dark brown papules on face and neck. They common in people with darker skin tones. Their appearance is identical to small seborrhoeic warts.

They are usually round although they can also be oval in shape. Some seborrhoeic warts have an irregular shape. Their size can vary from around one centimetre to several centimetres in diameter.

Black pigmented verrucous lesion

© Alborz Fallah, CC BY-SA 3.0, via Wikimedia Commons

Seborrhoeic keratosis

© Lmbuga, Public domain, via Wikimedia Commons

Seborrhoeic warts tend first to appear around the age of 40. They can sometimes run in families. The actual cause of seborrhoeic warts is unknown. It can be common to develop several seborrhoeic warts as you become older. Also, as time goes by, each wart tends to grow slightly and become darker. They can occur anywhere on your body, other than on your palms or soles, and there may be multiple lesions.

No. Seborrhoeic warts are always benign. That means they do not spread and they are not cancerous. The main problem is that they can sometimes look unsightly, particularly if they develop on your face.

However, rarely, seborrhoeic warts may be associated with various cancers. The Leser-Trélat sign is rare and refers to the sudden appearance of multiple seborrhoeic warts. This sign is associated with a number of different cancers, particularly bowel, breast, or stomach, and has also been associated with cancers of the liver, kidney and pancreas.

Very rare cases have been reported of a type of skin cancer called melanoma developing within a seborrhoeic wart. It is not known if this is just a coincidence or whether it represents a true cancer change in the seborrhoeic wart. If you do notice a change in a seborrhoeic wart, it is worth asking your doctor to examine it.

Note: although they are called warts, they are not caused by the wart virus. They are not infectious.

Doctors can often diagnose seborrhoeic warts by their appearance. However, if there is any doubt about the diagnosis, especially if the possibility of a more serious diagnosis such as skin cancer is suspected, then dermatoscopy may be used for a closer look at the structure of the lesion.

Dermatoscopy is a technique to examine the skin with a magnifying lens and a light. It can help diagnose skin lesions by accurate assessment of their colour, structures, patterns and borders.

Sometimes a biopsy or removal of the lesion may be needed so that the diagnosis can be confirmed by the detailed structure of the lesion (histology).

If they do not cause any problems then it is best that they be left alone. Without treatment, they usually continue to grow and can become darker and more crusty. However, they do increase in size very slowly.

If required, however, they can be removed quite easily. Seborrhoeic warts are usually removed because they itch, they interfere with clothing or jewellery or they are unsightly.

Two commonly used methods to remove them are:

• By using a curette. This involves 'freezing' the surrounding skin with local anaesthetic. The seborrhoeic warts are then scraped off with a sharp surgical instrument called a curette.

• Liquid nitrogen treatment. Liquid nitrogen is very cold and anything it touches is killed by the cold. Small amounts of liquid nitrogen can be sprayed on to small seborrhoeic warts. The seborrhoeic warts are killed and drop off a few days later. Normal skin replaces the area left behind. Liquid nitrogen is not suitable for larger warts.

Once seborrhoeic warts have been removed, they usually do not return.

Seborrhoeic warts do not become cancerous and are benign, unless there is a sudden appearance of multiple seborrhoeic warts, which may be associated with various cancers (see Leser-Trélat sign above).

Seborrhoeic warts way cause minor local complications such as infection, bleeding or surrounding dermatitis (eczema).