MONDAY, June 20, 2005 (HealthDayNews) -- While people have become aware of the dangers of skin cancer, the most serious type of melanoma is often missed in its early stages, researchers report.
Nodular melanoma, the most aggressive type of skin cancer, makes up 9 percent of all cases and 34 percent of thick melanoma cases. In contrast, the most common melanoma, superficial spreading melanoma, is usually diagnosed early and typically is a thin melanoma.
The difference between thick and thin melanomas is simply that thin melanomas tend to spread out over the surface of the skin, while thick melanomas grow down into the skin.
The incidence of melanoma in the United States has risen sharply from 1969 to 1999, and that increase is disproportionately greater in men 65 and older. Deaths from melanoma are strongly associated with the thickness of the primary lesion, according to the report in the June issue of the Archives of Dermatology.
"When we look at melanoma, the percentage of nodular melanomas has not moved over 12 years," said study author Dr. Marie-France Demierre, director of the Skin Oncology Program at Boston University School of Medicine.
To determine trends in distribution of thin and thick melanomas from 1988 to 1999, Demierre and her colleagues looked at skin cancer data from the Surveillance, Epidemiology, and End Results (SEER) database.
The researchers found the number of new melanoma cases increased 60 percent during that time. From 1988 to 1991, there were 9,132 cases, and from 1996 to 1999, there were 14,575. Meanwhile, the proportion of thick melanomas (at least 2 millimeters thick) remained practically unchanged during the 12 years of the study.
Demierre believes the reason many of the thick, nodular melanomas are missed is that they don't fit the criteria that many people and their doctors have learned to recognize as skin cancer. People have been taught to identify skin cancer by using the ABCD criteria: A for asymmetry; B for border irregularity; C for color change; and D for diameter change.
"Really, a lot of melanomas present without any of the ABCD," Demierre said. "The moles become itchy, the changes are small, and those turn out to be the thicker melanoma, often the nodular melanoma," she added.
To deal with this problem, Demierre said that people need to be more aware of the changes in any mole.
"If you have a lesion that you are concerned about, you should have it checked," she advised.
On expert agrees that more needs to be done to get people to recognize the thick, nodular melanomas.
"We have done a pretty good job on getting people to identify superficial spreading lesions," said Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society. "But we really haven't really done as good a job on the nodular side."
Just because a lesion doesn't meet the ABCD rule doesn't mean you shouldn't get it checked, Lichtenfeld said.
"The bottom line is, if you have a lesion on your skin, and it's changing -- that is, it's getting larger, changing color, appears to be raising -- go see your doctor and get it checked. And you need to get there quickly, because this lesion grows fast," he stressed.
Three other reports in the same issue of the journal shed light on several aspects of melanoma.
In the first report, researchers looked at microsatellites to see if their presence was predictive of survival after being treated for skin cancer. Microsatellites are nodules of melanoma cells that are away from the main body of the tumor.
The research team led by Dr. Mohammed Kashani-Sabet, from the Melanoma Center at the University of California, San Francisco, found that microsatellites do predict that cancer is likely to recur in the same area as the initial tumor, and that this recurrence does negatively affect survival.
In the second report, Case Western University researchers found that when sampling a melanoma for analysis, taking several samples of different thickness appears to be the best way to accurately classify the melanoma and guide doctors in their treatment choices.
In the third report, a survey of 1,200 dermatologists, researchers led by Dr. Allan C. Halpern, a dermatologist at Memorial Sloan-Kettering Cancer Center, found there are no standards among dermatologists for how wide an area around a melanoma should be removed. In addition, most dermatologists didn't know which melanomas were likely to progress and which weren't.
"Further research in the specific area of melanomas is warranted to develop clear guidelines in the management and prevention of further disease," Halpern's team concluded.
More information
The American Cancer Society can tell you more about skin cancer.
