The correct answer is A: Squamous cell carcinoma
Discussion: There is a common misconception among both the lay public and many health care providers of all types that those with darker skin tones are at no or minimal risk for the development of skin cancer. This misconception frequently leads to a delay in both proper diagnosis and expeditious treatment. While it is true that more deeply pigmented skin, because of its increased melanin content, possesses greater protection against ultraviolet radiation–induced neoplasia, it is a mistake to assign those who belong to the "skin of color" group to a "no risk" population. In fact, age-adjusted rates for melanoma are estimated at 4.5 per 100,000 among American Hispanics and 1 per 100,000 among African Americans. These rates, while lower than the estimated incidence of 21.6 per 100,000 among non-Hispanic American whites, are nonetheless of some concern. This is especially true considering an apparent rise in the incidence of melanoma diagnosed in those with darker skin tones. Equally reliable data regarding the incidence of nonmelanoma skin cancer among ethnic minorities is not readily available. However, nonmelanoma skin cancers certainly do occur, carry a significant burden, and impart substantial morbidity among both Hispanic and black patients.[3,4]
The delayed diagnosis of both melanoma and nonmelanoma skin cancer in people of color may also be attributable, in part, to the atypical locations where such lesions often arise. Both melanoma and nonmelanoma skin cancers occur most commonly on the routinely sun-exposed regions in non-Hispanic American whites. By contrast, Hispanics and African Americans experience a dramatically higher proportion of such tumors occurring in acral sites (hands and feet) and on the legs.[4-6]
Finally, a delay in recognition of melanoma and nonmelanoma skin cancer among ethnic minorities may be partially due to the perception of low risk common among individuals in these population subgroups. Poor risk perception leads to a lower rate of sun avoidance, appropriate sunscreen use, and regular cutaneous self-examination, as well as to a delayed presentation for medical evaluation and care.[7,8] This patient, for example, waited over 18 months before seeking medical attention.
Regarding this particular patient, melanoma might seem to be the most obvious clinical choice based upon the lesion's irregular outline and deep pigmentation. However, it is critical to recognize that among African Americans, nonmelanoma skin cancers are very often highly pigmented and thus may closely simulate a melanoma.[9,10] The actual diagnosis in this case, as verified by initial biopsy and eventual excisional histology, was pigmented Bowen disease (squamous cell carcinoma in situ) with a prominent focus of invasive squamous cell carcinoma. Because Bowen disease is much more common in Caucasians than in blacks, most of the generalizations regarding the presentation of this tumor are derived from the manner in which it manifests in non-Hispanic white patients. However, these generalizations simply are inaccurate in the case of black patients. For example, Bowen disease in African Americans is almost always heavily pigmented and preferentially favors the lower extremity.[11,12] This correlates well with this patient's presentation. Indeed, as recently summarized in the literature, among older African-American women, the specific clinical picture depicted here should be considered nearly pathognomonic for—or at least very highly suggestive of—squamous cell carcinoma in situ.
The differential diagnosis of pigmented Bowen disease of this size includes superficial spreading melanoma, pigmented superficial or invasive basal cell carcinoma, and giant seborrheic keratoses. These disorders can easily be differentiated on the basis of histopathology, and a biopsy is virtually always in order prior to designing definitive therapy.
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3. Rogers HW, Weinstock MA, Harris AR, et al. Incidence estimate of nonmelanoma skin cancer in the United States. Arch Dermatol. 2006;146:283-287.
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12. Rosen T, Tucker SB, Tschen J. Bowen's disease in blacks. J Am Acad Dermatol. 1982;7:364-368.
13. Woolery-Lloyd H, Elsaie ML, Avashia N. Squamous cell carcinomas of the lower limbs in African-American women. J Am Acad Dermatol. 2011;65:221-223.