“Doctor, how can I tell my mole isn’t a melanoma?”

I am often asked this question. Here are a few situations I have encountered in the office that help answer it. Details have been changed to protect patients' privacy.

A spot on the scalpA new patient came to see me for a dark spot on the scalp that a friend had noticed while styling the patient's hair. The spot was hidden under thick hair at the back of the head, where a person cannot see it themselves. My examination and the biopsy showed that it was a melanoma. Without that friend's attentive eye, the spot might have gone unnoticed.

A dark spot on the faceA person came to see me about a dark spot on the face. On dermoscopic examination, I noticed subtle abnormal signs and strongly suspected a melanoma, which the biopsy confirmed. That is why a pigmented spot of uncertain nature should always be diagnosed before any treatment is considered.

Two melanomas at the same timeOn one occasion, I found two melanomas in the same person during the same examination. Looking at all of the skin, and not only at the spot that is causing concern, can sometimes make the difference.

A second lookA person came in about a dark lesion on the lower back. It was a seborrheic keratosis, a benign lesion. While examining the rest of the back, I saw another, pinkish lesion a few centimetres higher. The biopsy confirmed my clinical suspicion: an amelanotic (non-pigmented) melanoma. Melanoma is often associated with a dark spot, but some melanomas are not dark.

What these situations show

To recognize a melanoma, the ABCDE rule is often taught:

• Asymmetry: the two halves of the spot do not match;
• Border that is irregular or poorly defined;
• Colour that is uneven, with several shades;
• Diameter larger than 6 mm;
• Evolving: the spot changes in size, shape or colour.

This is a good starting point, but not all melanomas follow this rule. A melanoma can be symmetrical, with well-defined borders. It can be a single colour, even pale or pink, as in the last situation. It can measure only a few millimetres. It can be recent or present for years. It can appear anywhere: on the scalp, the skin, the mouth, the genital area, the nails, the palms of the hands or the soles of the feet. It can also be found in the eye, but that is another subject.

Melanoma does not have just one face, and it can look like a benign lesion. That is why, when I examine the skin, I use a dermatoscope, which works like a magnifying lens, to see the details of lesions that leave me with a doubt.

When to have a lesion examined

The vast majority of skin lesions are benign. The goal is not to worry about each one, but to know which ones to have examined.

I often tell my patients: if a skin lesion is new, changing, bleeding, itchy, painful, does not look like its neighbours, or leaves you in doubt, have it examined. The same goes for a small, firm bump that has been growing for more than a month, even if it is pink or skin-coloured.