The Asian Dermatologic Patient: Review of Common Pigmentary Disorders and Cutaneous Diseases

Stephanie G.Y. Ho; Henry H.L. Chan

Disclosures

Am J Clin Dermatol. 2009;10(3):153-168. 

In This Article

5. Cutaneous Malignancies in Skin of Color

The incidence of melanoma and non-melanoma skin cancers in the US is increasing yearly and may be partially attributable to UV exposure.[97] However, the higher melanin content in skin of color confers some photoprotection from UV-induced DNA damage. There also appears to be more efficient DNA repair mechanisms in skin of color, thereby reducing the likelihood of carcinogenesis.[7]

Public education campaigns to promote photoprotection and self-surveillance in individuals of all ethnicity can be beneficial in reducing the rates of cutaneous malignancies.

5.1 Melanoma

The incidence of melanoma has been reported to range between 0.2 and 2.2 per 100 000 in Asians. In a Singapore study, the incidence of melanoma was reported to be 0.2 per 100 000 in darker skinned Indians and 0.5 per 100 000 in fairer skinned Chinese.[98] In Hong Kong, melanoma incidence was reported to be 1.1 per 100 000 women and 1.0 per 100 000 men.[99] The Japanese have roughly double the incidence of melanoma (2.2 per 100 000) than other Asian races.[100]

In skin of color, the most common sites for the development of melanoma are non-sun-exposed areas, such as palmar, plantar, subungual, and mucosal surfaces. In a study of 43 cases of melanoma in Chinese patients at the University of Hong Kong from 1964 to 1982, 56% of tumors arose from the foot, with 83% occurring on the plantar surface (figure 5).[101] Forty-seven percent of these tumors developed within an existing pigmented lesion, and 100% of subungual tumors involved the nail bed of the big toe or thumb. The most common histologic type was acral lentiginous melanoma with more than 80% having a Breslow thickness >3 mm and 37% of these ≥9 mm. A study from Japan also reported the foot as the most commonly affected area with 50% being the acral lentiginous melanoma type.[100] A large percentage also presented with advanced disease, with 30% demonstrating metastases and a poor prognosis.

Figure 5.

Melanoma on the plantar aspect of the foot.

Delays in diagnosis and treatment of melanoma are possibly due to lack of public and physician education and preventative screening programs in Asian countries. There is often a misconception that darker skinned individuals do not develop skin cancer. The sites of melanoma occurrence are also unexpected and difficult for patients to examine. In addition, acral tumors tend to be intrinsically more aggressive and therefore present at a later stage, leading to poorer prognosis.[102] Both physicians and patients therefore need to maintain a high index of suspicion for melanomas regardless of ethnicity and particular attention needs to be paid to palms, soles, fingers, toes, subungual areas, and mucosal surfaces in Asian patients.

5.2 Non-Melanoma Skin Cancer

Basal cell carcinoma (BCC), followed by squamous cell carcinoma (SCC), are the most common skin cancers in Chinese and Japanese individuals.[98,100,103] In Singapore, the incidence of BCC increased at a rate of 2.8% per year between 1968 and 1997, while the rates of SCC decreased by 0.9% yearly.[98] Chinese individuals, who are generally of lighter skin type, were twice as likely to develop BCC and SCC as the darker skinned Malays and Indians. In a survey conducted between 1983 and 1987 of the Japanese population living in sunny Hawaii, USA, the incidence per 100 000 was 60 for BCC, 48 for SCC, and 22 for Bowen disease.[104] The incidence of BCC in Japanese individuals living in native Japan was much lower, at 16.5 per 100 000, demonstrating the harmful effects of UV radiation.[105]

Known risk factors for BCC and SCC include UV exposure, Fitzpatrick skin types I-III, male sex, chemical and radiation exposure, burn or scar injuries, genetic disorders such as xeroderma pigmentosum, Gorlin syndrome, immunosuppression, and infection with human papillomavirus.[106] Photoprotection and early diagnosis can often lead to a better outcome.

5.3 Cutaneous T-Cell Lymphoma

Mycosis fungoides or cutaneous T-cell lymphoma is the fourth most common skin cancer amongst the Japanese.[106] Hypopigmented mycosis fungoides, with ill-defined, often pruritic, hypopigmented macules and patches, tends to present in a younger patient population and only in skin of color (figure 6).[107,108] The disorder can often be mistaken for vitiligo, pityriasis alba, tinea versicolor, or post-inflammatory hypopigmentation. Misdiagnosis can delay treatment. There is usually a good response to PUVA, UVB phototherapy, or topical mechlorethamine (chlormethine), but recurrences are common. The overall prognosis is good.[109]

Figure 6.

Hypopigmented mycosis fungoides.

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