ATYPICAL MELANOCYTIC NEVI OF THE GENITAL TYPE WITH A DISCUSSION OF RECIPROCAL PARENCHYMAL-STROMAL INTERACTIONS IN THE BIOLOGY OF NEOPLASIA

Melanocytic lesions of the genital area, especially those on the vulva , may present great difficulty in histological interpretation. A histo logical diagnosis of malignant melanoma was made in more than one thir d of 56 genital area melanocytic lesions submitted in consultation to the authors. The median age of the patients with these lesions was 25 years. This article is a clinicopathological study of these lesions an d distinguishes them from malignant melanoma, The stroma of the lesion s of the genital area was different from the stroma seen in the dyspla stic nevi and melanoma. The differences in the stromal form in the div erse lesions is useful in diagnosis and is of profound biological sign ificance. The stroma in the reported lesions and in some lesions of me lanocytic neoplasia is described in detail, and its biological signifi cance is discussed, Three sets of cases are used in this comparative s tudy to delineate the clinicopathological nature and the biology of th e genital nevi. The 56 cases submitted in consultation constitute the primary series of our work (The Clark Cutaneous Pathology Laboratory S eries). These are compared with a series of cases from the Pigmented L esion Group of the University of Pennsylvania and Pathology Services, Inc, and another series of cases from the Genetic Epidemiology Branch of the National Cancer Institute. The two series used for comparative study contain approximately the same number of cases of dysplastic nev i and malignant melanoma as there are atypical melanocytic nevi of the genital type in the primary series. The total number of eases was stu died by comparison of their attributes in a relational database, The c linical data of the primary series was acquired through the use of a q uestionnaire completed by the contributors. The 56 cases presented two distinctive pathological pictures, One of these is termed atypical me lanocytic nevi of the genital type (AMNGT),whereas dysplastic nevi (DN ) formed the second of the two pathological pictures. There were 36 AM NGT and 14 DN. The remaining six cases were common nevi without atypia or ill-defined melanocytic hyperplasias. The lesions of AMNGT are usu ally located on the vulva, but they are seen on the perineum and, rare ly, on the mons pubis and in the axilla. Lesions similar to AMNGT have been seen uncommonly on the male genitalia. The stromal patterns were distinctive and related to specific melanocytic lesions. An unclassif ied (unclass) or nonspecific stromal pattern was associated with AMNGT ; a pattern of regression with differentiation (diff-regress) dominate d the stroma of common dermal nevi; concentric eosinophilic fibroplasi a (cef) and lamellar fibroplasia (If) were present in dysplastic nevi; fibroplasia with a plaquelike lymphocytic infiltrate (fl) and diffuse eosinophilic fibroplasia (def) were noted in radial growth phase mela noma; and fibroplasia with angiogenesis (fa) or an absence of evidence for parenchymal stromal reciprocal interactions (nopsi) marked thick or deeply invasive vertical growth phase melanomas, Recommendations fo r management of the lesions are suggested. Conclusions: One kind of at ypical melanocytic proliferation in the genital area forms a distincti ve clinicopathological entity that can be distinguished from melanoma and dysplastic nevi, the AMNGT. Such lesions are more common on the la bia minora or the mucosa of the clitoral region than they are on the l abia majora. The other common atypical melanocytic proliferation of th is area is a dysplastic nevus, which is much more common on the labia majora than on the labia minora. The reciprocal interactions between p arenchyma and stroma are discussed as homeostatic processes, a continu ally functioning template maintaining tissue, organ, and organismal fo rm and function. The progressive disorganization of this template in n eoplasia is illustrated and is considered to be a cardinal element in the biology of neoplasia. Copyright (C) 1998 by W.B. Saunders Company.