New guidelines could help pathologists more consistently diagnose the severity of invasive melanoma. Photo by UCLA/BMJ

May 18 (UPI) -- Researchers with the American Joint Committee on Cancer have updated the guidelines for determining the severity of individual cases of a type of serious skin cancer known as invasive melanoma.

Judging the severity of a tumor growth, called "cancer staging," isn't easy. Research shows pathologists, after looking at the same imaging of the exact same tumor, regularly disagree on the cancer's staging.


During a previous study of invasive melanoma staging based on the old guidelines, researchers found pathologists disagreed more than 50 percent of the time. With their update, researchers hoped the guidelines would produce greater consensus among pathologists.

To test their new guidelines, researchers recruited the same pathologists from the previous study to review -- unbeknownst to them -- the same melanoma images.

When using the new AJCC 8 criteria to judge the severity of the invasive melanoma, pathologists agreed with the consensus of an expert panel of dermatopathologists 54 percent of the time, up from 44 percent using the AJCC 7 criteria.

The results of the study were published this week in the new journal JAMA Network Open.

"Pathologists may be able to more accurately classify invasive melanoma using the new guidelines," researchers wrote in a news release. "Although there was only slight improvement in how often pathologists agreed on characterizing invasive melanoma, that difference could help improve treatment outcomes for some patients."