It Is Not About How Many Moles You Have: the Ugly Duckling Rule and the Five Letters Dermatologists Look For After Summer

It is not about how many moles you have. It is about whether one of them looks different from all the others. Paloma Cornejo, a dermatologist and head of the Más Que Derma clinic, calls this the ugly duckling rule - and it is the fastest test anyone can run at home after summer.

The logic is the reverse of what we expect

In most people, moles resemble one another: similar size, round or oval shape, roughly the same shade of brown. That is the normal for that particular body. When one mark stands out from that pattern - larger, a different shape, a different colour - that is the ugly duckling, and that is the signal to see a doctor.

It matters that this is not self-diagnosis. Standing out can mean seborrheic keratosis, an atypical naevus, a carcinoma or a melanoma - four entirely different diagnoses. The job of the person at home is not to guess which one it is, but to notice it.

ABCDE - and the letter that counts most

The second rule is well known: A for asymmetry - one half looks different from the other; B for borders that are irregular or blurred; C for colour, when one mark contains several shades; D for diameter; E for evolution.

She calls the last the most important. A mark that grows, loses its symmetry or changes colour needs an examination - regardless of how it looks at that moment. In other words: this is not a photograph, it is a film. What matters is what has changed since last year.

The places nobody looks at

She lists the areas that regularly get skipped: between the toes, the soles of the feet, the scalp, the genital area and the back. Of the back she says it is almost impossible to check alone - simply because a person cannot turn that far round. The solution is for somebody else to look, or to photograph it.

Another common misconception: melanoma does not have to appear on an existing mole. It can show up as a new mark that looks different from all the others from the very start.

Who should look more often

People who have already had skin cancer, a family history of melanoma, sunburn in childhood, a large number of moles or a fair phototype. For them a regular examination is not caution, it is routine.

The dermatoscope - the magnifier that shows details the naked eye does not have - is why a self-check is not a substitute for a doctor. But it is not useless either: it is what decides whether the appointment gets made at all. The end of summer is a good reminder, though Cornejo herself says any time is a good time. The question is when anyone here last booked an appointment for something that does not hurt.