Skin cancer in skins of color

In recent years medical healthcare professionals have made strides to raise awareness about skin cancer. Despite these efforts, the false notion that non-Caucasian individuals are exempt from this disease is still espoused by many physicians and patients. Primarily as a direct result of delayed diagnosis, these populations often have a poor prognosis when afflicted with skin cancer. Nearly 1 in every 10 of the 3141 counties in the US has a minority population greater than 5:0 percent.(1) This demographic and coupled with the fact that skin cancer is generally a curable disease make it impossible to ignore the higher mortality rates seen in people of color who have a cutaneous malignancy. Dermatologists should become acquainted with the epidemiology of skin cancer in skins of color, so these patients receive the educational information which promotes understanding and prevention of this disease.

Along with their respective colleagues, Drs. Rebat Haider and Hugh Gloster have published extensively on this topic. Below is largely a condensed review of their findings.

Not All Skin is Created Equal

Literature dating back to 1957 provides evidence that, as it pertains to the histological makeup of the integument, not all skin is created equal.(2) Differences in both the size and distribution of epidermal melanosomes determine an individual's vulnerability towards ultraviolet (UV) light.(2-5) Smaller, less dense, grouped melanosomes, which are more prevalent in the keratinocytes of Caucasians, are less effective at blocking UV light, In contrast, larger, denser, and less aggregated melanosomes found in the epidermis of darker skinned people afford more protection against the deleterious and carcinogenic effects of sunlight. It follows that when people of color do get squamous cell carcinomas (SCCs) or malignant melanomas (MMs), incidents usually occur in sun-protected areas, suggesting an etiology other than UV radiation. The exception to this rule is in the case of basal cell carcinoma (BCC), which arises primarily on sun-exposed skin in all ethnic groups.(6), (7)

Nonmelanoma Skin Cancer

The Americas

Basal cell carcinoma is the most common skin cancer amongst Caucasian and Hispanic populations. It is the second most frequently occurring cutaneous malignancy in African Americans.(2), (7), (8) The incidence of BCC per 100 000 people amongst various North American ethnic groups is as follows: Caucasians in Kauai, Hawaii (262); Caucasian men (250); Caucasian women (212); New Mexican Hispanic men (171); New Mexican Hispanic women (113); Southeastern Arizona Hispanic men (91); Southeastern Arizona Hispanic women (50); African American men (1); African American women (2)(7) (Figure I).

In distinct contrast to SCC and MM, UV light seems to be inextricably linked to the development of BCC in all skin types despite pigmentation, and does not result in increased mortality.(6), (7) Subsequently, at presentation, non-Caucasian patients with BCCs share a similar phenotype with their Caucasian counterparts: most are persons 50 years old or greater with a lesion on photo-exposed skin.(6), (7) A study at Howard University revealed that BCCs arising in brown skin occur on the head and neck at a rate of 89%.(9) The correlation between UV light and BCCs in darker skin types also explains the relatively higher incidence of this malignancy amongst darker skinned populations living in warmer climates, such as Hispanics residing in New Mexico and Arizona.(7), (10) Both African Americans and Hispanics present with BCCs of many histological subtypes, although the mor-pheaform variant is particularly uncommon, especially in African Americans(6) Pigmentation is present in greater than 50% of BCCs found in skins of color versus 6% in Caucasian skin.(7) In a study by Bigler et al, 30 BCC biopsy specimens from patients with Hispanic surnames were compared with 30 BCC biopsy specimens from patients with Northern European surnames. Results revealed that pigmented BCCs were twice as common in Hispanic patients.(6), (11) Another review indicated that when Hispanic patients do get BCCs, they have a propensity to have multiple lesions either at the time of presentation or in the ensuing years.(6) These additional tumors occurred as soon as I year, and long as 10 years after the initial diagnosis.(6) In addition to the sun, other preexisting conditions can increase minorities' predisposition for developing BCC: previous radiation therapy, albinism, trauma, chronic scarring processes, arsenic exposure, nevus sebaceous, and genodermatoses such as basal cell nevus syndrome and xeroderma pigmentosum.(6), (7), (9)

Squamous cell carcinoma is the most common skin cancer amongst African Americans.(6), (7), (9), (12) The incidence of SCC per 100 000 population is Caucasian men (195), Caucasian women (84), Caucasians in Kauai, Hawaii (118), New Mexican Hispanics (21), Southeastern Arizona Hispanics (23), and African Americans (3)(7) (Figure 2). Squamous cell carcinoma occurs on the head and neck of darker skinned, non-Caucasian people approximately 35% of the time according to one review.(13) This supports the premise that when it comes to populations with brown skin, UV radiation does not seem to play a formidable role in SCC carcinogenesis. A retrospective chart review performed over a 5-year period in Atlanta, Ga helped to further elucidate the clinical nature of and predisposing factors for these seemingly unique SCCs occurring in African Americans.(14) Squamous cell carcinoma was identified in 35 patients. Although some of the cancers did occur on the photo-exposed sires of the head, neck, and arms; the overwhelming majority were found on the photo-protected skin of the legs and anogenital region. Interestingly, amongst the African American patients, only males were found to have SCC in the anogenital region, and only females (age range: 32-101 years) were found to have SCC on their legs. These cohorts of African American females with SCC of the legs were found to have commonalities as it pertained to the presentation of their disease. More specifically, the SCCs found amongst these women were largely accompanied by perilesional mottled dyspigmentation, halt of the lesions were hyperpigmented, and many were accompanied by smaller hyperkeratotic plaques thought to appear clinically similar to seborrheic keratosis, verruca vulgaris, and actinic keratosis. Clinicians should thus be aware of this constellation of findings in African American patients, as they may herald a cutaneous malignancy.