Seborrhoeic keratosis (SK) are benign lesions that arise from the epidermis of the skin. They are extremely common in older people and sometimes referred to as seborrhoeic warts, senile warts, basal cell papilloma and senile keratosis.
The biggest problem with SK is their appearance and the feel of the skin lesions, as they can sometimes be itchy and become irritated and inflamed.
Seborrhoeic keratosis is sometimes confused with melanoma or vice versa, especially when very darkly pigmented.
Who gets seborrhoeic keratosis?
SK occur in the middle-aged and elderly with increasing prevalence. They can rarely be solitary, but there are usually multiple.
There is a genetic predisposition, and they occur equally in men and women. Sunlight may play a role, but it can be found in areas not exposed to the sun.
What does SK look like?
Although they vary in appearance, the below are indications of seborrhoeic keratosis:
- Well-demarcated lesions and appear as if they are ‘stuck on’ the skin.
- They range in colour from white to dark brown and almost black.
- They can be flat and barely palpable and stay that way or become raised, rough, irregular or pedunculated over time.
- SK occur in all areas, i.e. the face, scalp, trunk and legs; however, they do not generally appear on the palms and soles.
- Sometimes, SK can be accidentally scratched off.
Due to their variable colour, shape and irregularity, they can sometimes be mistaken for melanoma. In addition, verruca vulgaris (viral warts) are also very similar in appearance to seborrhoeic keratosis.
Are there different variants of seborrhoeic keratosis?
There are several SK variants, including:
- Solar lentigo: Also known as an old-age spot, they are harmless patches of darkened skin.
- Dermatosis papulosa nigra: Tiny moles on the face and neck.
- Stucco keratoses: Papules found on the lower extremities that are grey, white or yellow in colour.
- Inverted follicular keratosis: Commonly found on the face and sun-exposed areas of elderly patients, typically on the upper eyelid.
- Large cell acanthoma: A slightly scaly, tan macule on sun-damaged skin.
- Lichenoid keratosis: Usually a small, solitary, inflamed macule or thin pigmented plaque.
Can seborrhoeic keratosis become cancerous?
SK are benign lesions, but rarely they can be found in association with skin cancers. We call this a collision lesion, i.e. where two separate lesions occur in the same area of skin.
How do you treat SK?
The treatment of seborrhoeic keratosis is unnecessary but can be done for cosmetic reasons or if the SK has become itchy, irritated and inflamed, or atypical in appearance. In the latter case, your doctor will want to rule out skin cancer.
What are the treatment options for SK?
Seborrhoeic keratoses can be removed if you are unhappy with their appearance or if they have become irritated.
- Cryotherapy (liquid nitrogen) where appropriate and where there is a low risk of causing scarring and hypopigmentation.
- Cauterisation of smaller lesions with a local anaesthetic.
- Curette and cautery of larger lesions.
It is sometimes necessary to send a lesion for histology to exclude any co-existing cancerous lesions.
Seborrhoeic keratosis can remain flat and barely visible throughout life, or they may become raised, rough and irregular. Unfortunately, it is not possible to predict which ones will grow and which will remain barely visible.