Comparison of Acral Nevomelanocytic Proliferations in Japanese and Whites

Randall J. Margolis, Arthur K.F. Tong, Hugh R. Byers, Martin C. Mihm
1989 Journal of Investigative Dermatology  
T he relative incidence of acral lentiginous melanoma appears much less in whites than in Japanese [1]. However, in both groups, deeply invasive malignant melanoma is associated with a high risk for metastasis, and the early diagnosis of malignant melanoma may result in a better prognosis. To identify any morphologic features that may, in the future, be evaluated in order to determine whether or not they have any epidemiologic and/or prognostic significance, a study of nevi and malignant
more » ... nd malignant melanoma from Japanese was under taken utilizing cases from the consultative practice of one of us (MCM) between 1977 and 1987. These cases from Japanese pa tients were compared and contrasted with benign, atypical and ma lignant nevomelanocytic lesions in whites. Acral lentiginous melanoma in Japanese and whites is an example of a lentiginous melanocytic proliferation that has evolved into an invasive malignant melanoma. Lentiginous melanocytic prolifera tions, in our view, describes an increased number of nevomela nocytes singly dispersed along the dermal-epidermal junction, whether or not there is epidermal hyperplasia. As a point of refer ence and in order to better understand the features of these lesions, the more common types of lentiginous melanocytic proliferations in whites will be reviewed. These include lentigo, the dysplastic nevus, and lentigo maligna. Lentigo Simplex Lentigo, or so-called lentigo simplex, is a uni formly colored, well-demarcated, tan to dark brown, round to ovoid lesion. It is usually 5 mm in diameter and occurs anywhere on the body surface, including mucosa. Histologically, it has uniform elon gation of the rete ridges of the epidermis along with increased ketratinocytic pigmentation as well as proliferation of the nevome lanocytes along the dermal-epidermal junction that sometimes forms nests at the tips of the rete ridges [2, 3] . This clinicopathologic type of lesion has also been described in the Japanese population. Dysplastic Nevus The dysplastic nevus is a clinical and patho logic entity that is associated with a familial tendency to develop dysplastic nevi and malignant melanoma. Clinically, these lesions Reprint requests to: Martin C. Mihm,]r., M.D., Dermatopathology Divi sion, Massachusetts General Hospital, Boston, MA 02114. that in the Japanese group the melanocytes in benign and atypical proliferations are less dendritic than those noted in whites, and, in both groups, extensive pigmentation was noted in both the epidermal and dermal components of be nign and malignant lesions in this limited review. A practical approach to classifications of atypism is, likewise, offered. ] Invest DermatoI92:222S-226S, 1989 have a mottled, slightly irregular color along with irregular, poorly demarcated borders, and they are often associated with a preexist ing, raised nevus. In addition, there is striking variability from le sion to lesion. Histologically, the lesions show a constellation of changes. The first is a lentiginous proliferation of atypical nevomelanocytes whether appearing de novo or in association with a preexisting compound or dermal nevus. In the presence of a preexisting nevus, the basilar proliferation of nevomelanocytes must extend greater than three rete ridges beyond the dermal component in order to qualify for the designation of dysplastic nevus. This extension iden tifies the so-called shoulder effect. The intraepidermal nevomela nocytes characteristically are large, ovoid or fusiform cells with ample cytoplasm, prominent nuclei, and obvious nucleoli, whereas the dermal nevomelanocytes are about the size of a lymphocyte with very scant cytoplasm, and uniform round nuclei. The second criterion involves the epidermal and dermal nests of nevomelanocytes associated with the lentiginous nevomalanocytic hyperplasia. The epidermal nests of nevomelanocytes are dispersed along elongated rete ridges with "bridging" of nevomelanocytes between rete ridges, and the dermal nevomelanocytes are more typically seen as sheets of cells rather than discretely grouped nests. The third criterion involves a constellation of stromal changes. These changes include lamellar fibroplasia and/or concentric eosin ophilic fibrosis about the elongated rete ridges. There is also in creased vascularity, a dermal mononuclear cell inflammatory infil trate, and, often, numerous melanophages in the dermis [4] [5] [6] [7] . Lentigo Maligna This irregularly pigmented macular lesion of the elderly occurs exclusively in sun-exposed areas. It has varied color that includes tan, brown, and even dark brown/black. Some times there are areas of depigmentation at sites of spontaneous re gression. When raised areas occur, invasive malignant melanoma has supervened [8, 9] . Histologically the lesions show atrophy of the epidermis along with a proliferation of strikingly pleomorphic nevomelanocytes along the basilar region of the epidermis with extension down the external root sheath of hair follicles and eccrine ducts. The pleo morphism of nevomelanocytes, especially in the earlier lesions, is very reminiscent of the lentiginous melanocytic hyperplasia seen in 0022-202X/89/S03.50
doi:10.1038/jid.1989.69 fatcat:m52mtpcvg5bulkxzn4qqyb4uqa