(CNN) Popular smartphone apps that assess suspicious moles on people's bodies may not be reliable in detecting all forms of skin cancer, doctors have warned.
A study found that the leading apps were both missing melanomas and incorrectly telling people their moles were a cause for concern.
The researchers evaluated SkinVision and SkinScan, two popular European apps which have not yet been approved for a launch in the United States by the Food and Drug Administration (FDA).
"Our review found poor and variable performance of algorithm-based smartphone apps, which indicates that these apps have not yet shown sufficient promise to recommend their use," wrote the authors, from the universities of Birmingham and Nottingham in the United Kingdom.
They warned that the current regulatory processes "are inadequate for protecting the public against the risks created by using smartphone diagnostic or risk stratification apps."
And they noted that healthcare professionals "need to be aware of the limitations of algorithm-based apps to reliably identify melanomas, and should inform potential smartphone app users about these limitations."
The World Health Organization estimates that between two and three million non-melanoma skin cancers and 132,000 melanoma skin cancers occur globally each year.
But skin cancers are generally treatable when diagnosed early, which the authors said makes prompt and accurate detection "crucial." Nine previous studies, which analyzed six different apps, were reviewed.
The largest risk factor for melanoma is overexposure to ultraviolet radiation, from sun exposure or using sunbeds.
Despite public health efforts to raise awareness of the risk -- particularly in hotter countries such as Australia -- another study in 2018 found that worldwide, men are dying from skin cancer at a higher rate than women and that the overall rate of diagnoses had risen in recent decades.
Melanoma has the highest mortality rate of skin cancers, according to the paper, and accounted for 1.7% of all cancer diagnoses worldwide during the time period they observed.