Melanomas are more likely to grow rapidly if they are thicker, symmetrical, elevated, have regular borders or have symptoms, according to a report in the December issue of Archives of Dermatology.

In addition, rapidly progressing melanoma is more likely to occur in elderly men and individuals with fewer moles and freckles, and its cells tend to divide more quickly and have fewer pigments than those of slower-growing cancers.

“Anecdotal experience suggests that there is a form of rapidly growing melanoma, but little is known about its frequency, rate of growth, or associations,” the authors wrote as background information in the article.

One previous study suggested that how quickly a melanoma grew predicted how likely the patient was to relapse at one year or to survive without relapsing. Other research indicates that different types of melanoma grow at different rates; for instance, an aggressive type known as nodular melanoma grows more quickly than any other kind.

Wendy Liu, PhD, Peter MacCallum Cancer Center, East Melbourne, Australia, and colleagues investigated melanoma growth rate in 404 consecutive patients (222 male, 182 female, average age 54.2 years) with invasive melanoma.

Participants’ skin was examined by a dermatologist and information about such characteristics as the number of typical and atypical moles was recorded. In addition, patients were interviewed as soon as possible after diagnosis and preferably in the company of a friend or family member. Researchers gathered information about demographics, skin cancer risk factors, the characteristics of the tumor and who first detected the cancer?the patient, a family member or friend, or a physician.

In addition, all patients and their families were asked to recall the date at which they first noticed a spot on their skin from which the melanoma later developed and the date at which they noticed the marking had changed or become suspicious.

The researchers used these two dates, the date that the melanoma was removed as obtained from medical records, and the thickness of the tumor at the time of removal to estimate the approximate rate of growth. This method was double-checked by comparing the rate of growth with the tumor mitotic rate. Tumors with a higher mitotic rate also had a faster rate of growth as determined by the researchers’ formula.

Approximately one third of all melanomas (141) grew less than 0.1 millimeters per month, another one third (136) grew between 0.1 millimeters and 0.49 millimeters per month, and one third grew by 0.5 millimeters or more per month. A high rate of growth was associated with tumor thickness, ulceration, amelanosis, regular borders, elevation, and symptoms.

Faster-growing melanomas were more likely to occur in individuals 70 years or older, in men and in those with fewer moles and freckles. Factors that were not associated with the rate of growth were the number of atypical moles or solar lentigines, history of sun damage or blistering sunburns, skin type, eye color, family or personal history of melanoma, and current or childhood sun exposure.

“In summary, this study provides descriptive data on the spectrum of melanoma rates of growth and insights into subgroups of patients with melanoma that are associated with rapid growth,” the authors concluded. “We propose that this information on melanoma rate of growth be incorporated into education programs for patients and health professionals.”