Unique clinical presentations in skin cancers among ethnic people can confuse physicians and perpetuate the problem of later diagnoses and higher mortality rates in darker-skinned individuals. Physicians should be particularly careful in checking feet and hands for possible signs of skin cancer, and use care not to confuse signs with those of other conditions.
New York - Studies in recent years have boosted awareness of the paradox of skin cancer among blacks and Hispanics: Their cancer rates are much lower than those of Caucasians, yet mortality rates are much higher. Whether heightened awareness has translated to the earlier diagnoses that are essential for better survival rates has yet to be seen.
A key problem contributing to the late diagnoses was that the low rates of skin cancer in people with skin of color translated to a lower level of suspicion among physicians and, therefore, less diligence in checking for the disease.
But even as awareness of the need to perform such exams grows, physicians may not even know what they're looking for.
Presentation of symptoms
"Basal cell carcinomas tend to be pigmented in people with skin of color," says Andrew F. Alexis, M.D., director, Skin of Color Center, St. Luke's-Roosevelt and Beth Israel Medical Centers, New York.
"And those pigmented basal cell carcinomas can sometimes be mistaken for seborrheic keratoses or dermatosis papulosa nigra (both benign lesions)," he says.
Regarding squamous cell carcinomas, Dr. Alexis says while they can be expected in sun-exposed areas of the skin in Caucasians, the opposite is true for darker-skinned people.
"Squamous cell carcinomas are more likely to be found on the legs and other relatively sun-protected areas in skin of color patients," Dr. Alexis tells Dermatology Times.
"In addition, they are more often associated with chronic ulcers or chronic scarring/inflammatory processes, rather than UV radiation (in contrast with Caucasians in which UV radiation from the sun is the most important risk factor)," he says.
Physicians should, therefore, use a high level of scrutiny in checking for SCCs in or adjacent to scarring or inflammatory processes such as discoid lupus, Dr. Alexis says.
Meanwhile, melanomas in dark-skinned patients are more likely to be found on the soles, palms, nail unit or mucous membranes. Again, those carcinomas can be mistaken for other problems.
Even when a diagnosis is accurately made, treatment - such as the use of cryotherapy for a nonmelanoma skin cancer - may need to be adjusted in darker-skinned patients.
"Cryotherapy would be a suboptimal choice in a darker-skinned patient, as it would result in considerable hypopigmentation," Dr. Alexis says.
While experts like Dr. Alexis work to improve awareness of the clinical aspects of skin cancer in darker-skinned patients, some research is helping to shed light on the underlying genetic distinctions of the condition.
One recent study offers intriguing data on the genetic features of melanomas that develop in sun-protected areas, such as the palms or soles.
The study considered that infrequent mutations of BRAF and NRAS genes occur in melanomas on mucosal membranes, acral skin (soles, palms and nail bed), and skin with chronic sun-induced damage.
Those genes are within the mitogen-activated protein pathway that is commonly mutated in melanomas on intermittently sun-exposed skin.
The study found oncogenic mutations in KIT in three of seven tumors, and mutations or copy number increases of KIT in 39 percent of mucosal, 36 percent of acral, and 28 percent of melanomas on chronically sun-damaged skin, but no increases in melanomas on skin without chronic sun damage.
The study concluded that KIT is an important oncogene in melanoma, and that since most KIT mutations found in melanoma also occur in imatinib-responsive cancer, the drug may offer a therapeutic benefit for melanoma. (J Clin Oncol. 2006 Sep 10;24(26):4340-4346. Epub 2006 Aug 14).
In addition to the emerging research, increased presentations and media attention have helped to improve awareness and understanding of distinctions between skin cancers in Caucasians and people with skin of color.
However, Dr. Alexis says, "Continued efforts are necessary to educate the public to be aware of the risk of skin cancers even in darker skin and to inform people with skin of color to be mindful of new or changing moles on the palms, soles or nails."