Originally published in The Ottawa Citizen October 12, 2004
Original Title: Out, Out Damn Spot Part Two

On Oct. 3, I reviewed why hyperpigmentation (dark skin spots) occurs, as well as some of the common causes and conditions. But it does not end there. Indeed, there are more skin conditions that raise many questions from concerned patients.

At the forefront in many people’s minds is whether a dark spot could be melanoma. Even with the increase in sunscreen use, the incidence of melanoma continues to grow. Early detection is vital to curing this disease.

If you are concerned about the appearance of a mole on your skin, the following “A-B-C-D-E” criteria for melanoma risk may be helpful:

Asymmetry: If the mole is divided in half by an imaginary line, both halves should appear identical for a non-cancerous (benign) mole.

Borders: The benign mole is usually round, having sharp, well-defined margins. A ragged, blurred, notched or uneven border is not normal.

Colour: A mole having a homogenous brown colour is normal. Multishaded moles or those that have a combination of colours such as blue, purple, red or black are suspicious for cancerous change.

Diameter: Moles greater than six millimetres (quarter inch) in diameter, about the size of a pencil eraser, are suggestive of melanoma.

Enlargement: A recent increase in the size of the mole warrants further investigation.

Any abnormal finding should be seen by your doctor.

Some may notice new skin growths that look like old bubblegum stuck onto the skin. They can be dark brown or black to tan in colour, have sharp borders and a surface that can be rough and craggy or smooth and pearly. These are seborrheic keratoses and are painless, benign and occur mostly in mid- to late-adult life. Removal is usually for cosmetic reasons unless it is rubbing on clothing, undergarments or other high-friction areas.

Obesity, Cushing’s syndrome, hypothyroidism and Type 2 diabetes, among other conditions, can lead to the development of small dark skin growths called acanthosis nigricans (Latin: dark thorn) in the skin folds of the neck, in the armpit, under the breast, in the groin or under the belt line. They can appear thick, leathery and wart-like, or a velvety brown streaking on the skin. The thick lesions can accumulate bacteria and give off a foul odour. A skin biopsy can confirm the diagnosis.

When acanthosis nigricans rapidly appears on the palms or soles of a non-diabetic patient, it may indicate that a cancerous tumour is growing somewhere. A thorough investigation will help determine if cancer is present. Most of these tumours (in order of incidence) are found in the stomach, colon, ovary, pancreas, rectum and uterus.

Treatment of acanthosis nigricans is directed at the underlying disease that initially led to the skin changes. If present, insulin resistance should be managed appropriately. Weight reduction will help eliminate the skin discolouration and improve the control of diabetes. Thick lesions with a bad odour can be cleaned with antibacterial soaps.

Diabetics can also develop a pimply pink or brown area called diabetic dermopathy. It will progress to a flat brown skin swelling that appears on the shins about 70 per cent of the time. Good sugar control can lead to their disappearance. Sometimes they do resolve spontaneously.

Darkening of the facial skin or melasma is distressing to many people. Certain hormonal medications, pheytoin (dilantin) and pregnancy can cause melasma by stimulating the skin to produce more pigment cells or melanocytes.

Treatment of melasma includes vitamin A acid creams, bleaching agents such as hydroquinone in combination with topical steroid creams and laser therapy. Avoidance of sun exposure can help prevent recurrence. Treatment success is variable and should be reviewed with your doctor.

Injured or traumatized skin can become more sensitive to pigment changes. The physical or chemical damage can cause a darkening or lightening of the skin. Indeed, exposing damaged skin to the sun can result in a permanent tanned patch.

The best advice is to talk to your doctor about any concerns you may have about skin discoloration. A general rule is the earlier it is assessed, the better the outcome.

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© Dr. Barry Dworkin 2004