Summary

Size has long been used as a guide when evaluating whether a skin lesion, such as a mole, might be cancer. An analysis of over 1,600 such lesions shows that those over 6 millimeters in diameter are over three times more likely to be cancer compared to smaller lesions. Therefore, the size criterion should remain as a significant element of the dermatologist's assessment.

Introduction

In 1985, a team of leading dermatologists in the United States devised the so-called ABCD criteria to help in the screening of skin lesions such as moles for melanoma, the most serious form of skin cancer. A is for asymmetry, B for border irregularity, C for color and D for diameter. Later, E was added for evolution, referring to the tendency for the lesion to change over time. The ABCDE guide is important not just to dermatologists but to the public as well. For the incidence of melanoma is increasing worldwide and you should be aware of any lesions appearing or developing anywhere on your skin.

Recently there has been some concern that the ABCDE criteria may lead to neglect of melanomas occurring from small lesions - those of less than six millimeters in diameter. Research has identified melanomas in such small lesions in populations from Italy, the United States, Australia and Israel. Small-diameter melanomas may account for three to 14 percent of all cases, although they tend to be less serious than those arising from larger lesions. So, the question arises as to whether small lesions ought to be subject to biopsy or not? As many as 99 percent of all skin biopsies turn out to be negative for melanoma, so modifying the guidelines to include smaller lesions could cause unnecessary patient anxiety as well as increasing healthcare costs. But what if melanomas are being missed by not carrying out biopsies on small lesions?

What was done

Doctors at New York University School of Medicine and colleagues elsewhere in the United States carried out the first study to show how the diameter of a biopsied skin lesion relates to the frequency of melanoma. Some of these dermatologists were involved in the development of the original ABCD criteria. They collected and analyzed data from 1657 lesions occurring in 1323 patients. The size of the lesion was measured prior to biopsy with a computerized skin-imaging system.

What was found

Of the 1657 lesions studied, 138 (8.3 percent) were diagnosed after biopsy as being melanoma, of which 54 were invasive. When it came to size analysis, 48.5 percent of the lesions were greater than 6mm diameter and the rest were 6mm or less in diameter. Within each 1mm diameter range between 2 and 6 mm the proportion of melanomas found did not vary. Between 3.6 and 4.5 percent of lesions within this diameter range proved to be melanoma. But from 6 to 7 mm diameter, 8.3 percent were melanoma. And among lesions 6 mm of larger in diameter, the proportion of melanomas ranged from 8.1 percent to 21.9 percent - roughly increasing as lesion diameter increased. Invasive melanomas accounted for 13 of 853 lesions that were less than 6 mm diameter and for 41 out of 804 lesions greater than 6 mm diameter. And in situ melanomas, which are confined to the skin's outer layers, were found in 2.6 percent of smaller lesions and 7.7 percent of larger lesions.

What this study means

The authors say that the striking relationship between the size of a lesion and the chance of it being a melanoma means that diameter should remain as part of the ABCDE criteria. It is also noted that the majority of lesions turn out to be benign. Having a biopsy of a suspicious skin lesion creates some anxiety for the patient and adds to healthcare costs. But it is better to be safe than sorry. Therefore, do continue to be aware of any moles or marks on your skin and use the ABCDE guidelines to know when medical attention is required.