III.12.1 Introduction
Pigmentation of the skin is determined at a cel- lular level. Although there may be some varia- tion in the number of melanocytes between races, this difference is not striking. There are approximately 2000 epidermal melanocytes per square millimeter on the head and forearm and 1000 epidermal melanocytes per square milli- meter on the rest of the body. These differences are present at birth [1]; thus, all persons have the same total number of melanocytes. It is the dis- tribution of melanosomes in the keratinocytes that correlates with skin color. In white skin, melanosomes are small and aggregated in com- plexes. In black skin, there are larger melano- somes, which are singly distributed within kera- tinocytes [2].
Interestingly, the distribution of melano- somes in black patients varies with the location on the body. In white patients, keratinocytes of both the volar and thigh skin demonstrate com- plexed melanosomes. Keratinocytes from the thighs of black patients demonstrate individu-
Chapter III.12
Melanocytic Lesions
in Darker Racial Ethnic Groups
Heather Woolery-Lloyd
III.12
ally separated melanosomes, whereas keratino- cytes from the lighter palmar surfaces of black patients have complexed melanosomes [3]. This finding further supports the theory that skin color correlates with the distribution of melano- somes, since the melanosomes in the light volar skin of black patients closely resemble the mela- nosomes of white patients.
III.12.2 Clinical Features III.12.2.1 Nevi
There are racial differences in the incidence and distribution of nevi in black and white patients (Table III.12.1). Studies of nevi in white patients range from an average of 14.6 to 61 nevi per pa- tient [4–6]. Studies of nevi in black patients range from 2.0 to 11 nevi per patient [5–8]; thus, it appears that nevi in black patients are less common than in white patients.
Interestingly, even within the black popula- tion, the number of nevi per patient differs. A study of black patients in New Orleans further subdivided the patients into fair, light-brown, and dark-brown groups. The authors reported a greater number of total body nevi in lighter black patients when compared with darker black patients [8]. This finding was different from a prior study which did not demonstrate any vari- ation in number of nevi within the black popu- lation [5]. The inconsistency between the two studies may be accounted for by a larger number of subjects in the New Orleans study and also, perhaps, a greater local variation in skin color in the New Orleans population. Another study in the Netherlands also demonstrated a steady de- cline in the median number of moles from fair
Contents
III.12.1 Introduction . . . .135
III.12.2 Clinical Features . . . .135
III.12.2.1 Nevi . . . .135
III.12.2.2 Melanoma . . . .136
III.12.3 Relevant Clinical Differential Diagnosis . . . .137
III.12.4 Conclusion . . . .137
References . . . .138
136 H. Woolery-Lloyd
III.12
skin to darker skin complexions [6]. From these data, it appears that as skin color increases, the total number of nevi on the body decreases.
The authors of the New Orleans study also examined the location of nevi on the body in the fair, light-brown, and dark-brown groups. This study revealed another interesting variation within the black population: They found a greater number of palmar-plantar nevi in dark- er black patients compared with lighter black patients (Fig. III.12.1). Similarly, mottled pig- mentation of the palms and soles was more fre- quent in the darker black patients. These data suggest that darker black patients have a greater number of acral melanocytic lesions compared
with lighter black patients. Histopathologically, these acral melanocytic lesions were most often lentigo simplex [8]. The average number of nevi on the palms and soles in the New Orleans black patients was 0.3 nevi. A study of 500 Nigerian healthy adults reported an average of one to three nevi per patient on the palms [9].
Acral melanocytic lesions in the black popu- lation are of special interest since this is the most common site of melanoma in black patients. In addition, clinical differentiation between acral lentigo and acral lentiginous mel- anoma can be especially challenging in darker- skinned patients.
III.12.2.2 Melanoma
The annual incidence of melanoma in black pa- tients ranges from 0.5 to 1.1 per 100,000 com- pared with 2–17 per 100,000 in white patients [10]. Melanomas are divided into four subtypes including nodular, superficial spreading, lentigo maligna, and acral lentiginous melanoma. Ac- ral lentiginous melanoma is the most common subtype of melanoma in black patients [10].
Melanoma can also be categorized by its lo- cation on the body. There have been suggestions that plantar melanoma, regardless of subtype, is more common in black patients than in white patients. In fact, the incidence of plantar mela- noma is equal among the races [11]; however, in black patients with melanoma, the plantar and palmar surfaces are the most frequent location.
In a study of 204 melanomas in black Africans, 86% presented on the palmar or plantar skin [12]. Subungal melanomas also represent a com-
Table III.12.1. Comparison of study results of distribution of nevi in white and black patients
White patients Black patients
Reference [4] [6] [5] [7] [8] [6]
Location New York The Netherlands New York Uganda New Orleans The Netherlands
Year 1952 1989 1963 1968 1980 1989
No. of patients 1000 62 208 260 251 12
Average nevi
per patient 14.6 61 2.0 11 8.3 8.5
Fig. III.12.1. This acral melanocytic nevus emphasizes
the importance of examining the interdigital space when
performing a full skin examination
Melanocytic Lesions in Darker Racial Ethnic Groups Chapter III.12 137
mon presentation of melanoma in black pa- tients. Nonacral cutaneous sites for melanoma are less common in black patients making the overall incidence of melanoma in black patients lower than in white patients [13].
Mucosal melanomas are another common presentation of melanoma in black patients.
These can occur on mucosal surfaces such as the oral, vulvar, and anorectal mucosa [14]. In contrast to cutaneous melanomas, these mela- nomas typically present later in life, after 60 years of age [15].
Although the incidence of melanoma is lower in black patients, melanoma is, in fact, a more lethal disease in this population. The California Cancer registry reported a 5-year survival rate for black patients of 70% compared with a sur- vival rate of 87% for white patients [16]. Another study examined melanoma survival rates at Washington Hospital Center. This study found a 5-year survival rate in African Americans of 58.8% compared with 84.8% in white patients [17]. Black patients were less likely to present with in situ/stage-I disease than white patients (39.3% vs 60.4%). Furthermore, black patients were more likely to present with stage-III/IV disease than white patients (32.1% vs 12.7%) [17]. Delayed diagnosis and treatment in black patients may explain the large disparity in sur- vival rates observed between these two groups.
III.12.3 Relevant Clinical Differential Diagnosis
Nonmelanoma skin cancers frequently present as pigmented lesion in darker skinned patients.
Most black patients with basal cell carcinoma present with hyperpigmented, translucent nodules on the head and neck [18]. Similarly, squamous cell carcinoma can present as a hy- perpigmented plaque in black patients. It is commonly described on the legs of elderly black women and can be confused with melanoma (Fig. III.12.2) [19].
III.12.4 Conclusion
In conclusion, there are many unique character- istics of melanocytic lesions in skin of color. The number of total body nevi appears to decrease with skin color, whereas the presence of pal- mar–plantar nevi increases with skin color. The latter observation may explain why the palmar and plantar surfaces are the most frequent loca- tion of melanoma in black patients.
It is also important to note that other skin neoplasms frequently present as pigmented le- sions in darker-skinned patients. Basal cell car- cinoma and, especially, squamous cell carcino- ma can be confused with melanoma due to their unique presentation in darker skin types. The unique features of pigmented lesions in darker skin types should be considered when examin- ing and treating patients of darker racial ethnic groups.
Fig. III.12.2. A pigmented squamous cell carcinoma in
an elderly African-American woman. This presentation
of squamous cell carcinoma can mimic melanoma
138 H. Woolery-Lloyd
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