A federal task force that assesses the value of medical screening tests says it cannot judge whether skin-cancer checks by dermatologists are worth the trouble for healthy Americans because good research on the practice is lacking.

The finding of the U.S. Preventive Services Task Force is not a repudiation of the practice recommended by the American Academy of Dermatology, in which a medical professional inspects a patient's skin for moles, thickening, discoloration or tags that might be cancerous. The task force says there are not enough well-conducted studies to establish that the practice saves lives without incurring undue risks for patients. The decision could influence health insurers not to cover skin-cancer screenings for people who have no history of the disease.

Each year, 5.4 million new cases of basal and squamous cell carcinomas are diagnosed, and while they are seldom fatal, they can cause disfiguration and metastasize to other parts of the body if left untreated. The most deadly form of skin cancer, malignant melanoma, is diagnosed in more than 76,000 new patients yearly, and claims the lives of 10,000 Americans a year. Its incidence is growing faster than any other preventable cancer's.

The finding prompted a chorus of concern. “Dermatologists know that skin cancer screenings can save lives,” the American Academy of Dermatologists said in statement Tuesday. Since the academy launched a skin cancer screening initiative called SPOTme 30 years ago, the academy said, dermatologists have performed more than 2.5 million screenings and found more than 255,000 suspected nonmalignant skin cancers and 28,500 melanomas.

“We know that screenings, which are noninvasive, quick and painless, are the best tool possible to detect skin cancer early when it is most treatable,” the academy said.

At the same time, the dermatologists' professional society wrote, “we acknowledge the need for additional research on the benefits and harms of skin cancer screening in the primary care setting.”

Writing in JAMA Oncology on the Preventive Services Task Force's recommendation, a trio of dermatologists pressed the case for continued screening.

Most patients — even those who have already been treated for melanoma, according to research — do not check their skin thoroughly for problematic growths, wrote a team of dermatologists led by Dr. Vinayak K. Nahar of the University of Mississippi. They overlook places where skin cancers can hide, or don't use a mirror to get a closer look, or don't enlist a loved one to help.

Patients do not really know what to look for, suggested Drs. Hensin Tsao and Martin A. Weinstock, dermatologists who wrote a JAMA editorial on the task force's finding.

The American Cancer Society recommends that primary care physicians check for skin cancer in all patients 20 or older during regular checkups. These doctors are armed with the helpful mnemonic “ABCDE” with which they are taught to look at moles for asymmetry, border irregularity, nonuniform color, diameter greater than 6 mm, and evolution over time.

But even these physicians, Tsao and Weinstock wrote, can overlook melanomas that look benign or masquerade as something else.

In deciding that it had insufficient evidence on which to base a recommendation, the federal task force said it found just one study of skin cancer screening, conducted in northern Germany, that found modest evidence that lives were saved. But the study's design was not the gold standard for weighing the risks and benefits of a biomedical intervention, and follow-up suggested that the benefits were even more modest.

Nahar and her colleagues said people were screened for skin cancer for only for a year in that study, which probably resulted in an undercount of the lives it saved.

They argued that the task force's “insufficient” finding could send a message of complacency about skin cancer.

“With melanoma's decades-long increase in incidence and slow-to-stabilize mortality, decisions must be made now,” the group wrote. “A recommendation stronger than [insufficient] is needed to emphasize screening as part of regular physical examinations,” the dermatologists wrote.