Title: Melanocytic nevus with focal atypical epithelioid components (clonal nevus) is a combined nevus
Abstract: To the Editor: We read with interest the article by High, Alanen, and Golitz1High W.A. Alanen K.W. Golitz L.E. Is melanocytic nevus with focal atypical epithelioid components (clonal nevus) a superficial variant of deep penetrating nevus?.J Am Acad Dermatol. 2006; 55: 460-466Abstract Full Text Full Text PDF PubMed Scopus (34) Google Scholar in the September 2006 issue of the Journal. The authors found that considerable clinical and pathologic similarities exist between cases of “nevus with focal atypical epithelioid component” (NFAEC) and those of “deep penetrating nevus” (DPN) that were studied. In fact, the only significant differences were as follows: (a) the extent of the lesions (NFAEC being confined to the superficial dermis, while DPN extended to the mid-reticular dermis or deeper); (b) the more common occurrence of a junctional melanocytic component in NFAEC; and (c) periadnexal spread being more commonly observed in DPN. Nineteen percent of the cases in this study showed overlapping histologic features of NFAEC and DPN. The authors suggest that the presence of the overlap group “may provide evidence that NFAEC and DPN lie upon a continuum; the chief determinant being depth of extension. On occasion, distinction may prove difficult, but would appear to be without clinical or prognostic significance.” Ninety-four percent of NFAEC and 84% of DPN in this study were associated with a coexistent common melanocytic nevus exhibiting so-called “congenital” features, as compared with 37% of “ordinary” compound or intradermal melanocytic nevi. In our experience at the Sydney Melanoma Unit, we have also frequently observed melanocytic tumors exhibiting the morphologic features of so-called NFAEC. The “focal atypical epithelioid components” in these lesions show considerable similarity to DPN, and we consider such components to be superficial variants of DPN, perhaps representing an earlier, more superficial stage of true DPN. These tumors usually include two discrete populations of nevus cells. For this reason, we report them as combined melanocytic nevi and describe the individual constituents (eg, compound melanocytic nevus and deep penetrating nevus components). In our series,2Scolyer R.A. Zhuang L. Palmer A.A. Thompson J.F. McCarthy S.W. Combined naevus: a benign lesion frequently misdiagnosed both clinically and pathologically as melanoma.Pathology. 2004; 36: 419-427Crossref PubMed Scopus (48) Google Scholar we found that the most common combination of components in combined nevi was a common (acquired or congenital) melanocytic nevus and a DPN (60.4% of 182 combined nevi studied); compound nevus of common acquired type and a DPN accounted for 31.3% of cases.2Scolyer R.A. Zhuang L. Palmer A.A. Thompson J.F. McCarthy S.W. Combined naevus: a benign lesion frequently misdiagnosed both clinically and pathologically as melanoma.Pathology. 2004; 36: 419-427Crossref PubMed Scopus (48) Google Scholar This is in line with High, Alanen, and Golitz's finding that the vast majority of their cases of NFAEC were associated with a coexistent melanocytic nevus1High W.A. Alanen K.W. Golitz L.E. Is melanocytic nevus with focal atypical epithelioid components (clonal nevus) a superficial variant of deep penetrating nevus?.J Am Acad Dermatol. 2006; 55: 460-466Abstract Full Text Full Text PDF PubMed Scopus (34) Google Scholar (ie, that they are in fact combined nevi). As detailed in our article,2Scolyer R.A. Zhuang L. Palmer A.A. Thompson J.F. McCarthy S.W. Combined naevus: a benign lesion frequently misdiagnosed both clinically and pathologically as melanoma.Pathology. 2004; 36: 419-427Crossref PubMed Scopus (48) Google Scholar we consider that other histopathologically similar tumors that have been reported under a variety of other terms including clonal nevus, inverted type A nevus,3Mihm Jr., M.C. Googe P.B. Problematic pigmented lesions. Lea and Feiger, Philadelphia (PA)1990Google Scholar and atypical dermal nodule in benign melanocytic nevus4Collina G. Deen S. Cliff S. Jackson P. Cook M.G. Atypical dermal nodules in benign melanocytic naevi.Histopathology. 1997; 31: 97-101Crossref PubMed Scopus (34) Google Scholar may also represent examples of combined nevi. The second atypical component of the aforementioned lesions probably also represents a component of deep penetrating nevus. It is our experience from reviewing many combined nevi (including so-called NFAEC) in our consultation practice that such lesions are a frequent cause of concern to patients, clinicians, and pathologists, and are often misdiagnosed clinically and/or pathologically as melanoma. Hence the report by High, Alanen, and Golitz provides a useful and timely reminder to pathologists of a potential diagnostic pitfall when reporting such lesions, especially when they exhibit an occasional mitotic figure. It remains unclear whether combined nevi (and NFAEC) represent the co-existence of two discrete nevus cell populations or whether they reflect divergent terminal differentiation of a single cell population. Some authorities have suggested that the tendency of combined nevi to involve the conjunctiva and eyelid and the occurrence of combined nevi with more than two distinct nevus cell populations support the divergent terminal differentiation hypothesis.5Crowson A.N. Magro C.M. Mihm Jr., M.C. The melanocytic proliferations: a comprehensive textbook of pigmented lesions. Wiley-Liss, New York2001Google Scholar Further evidence supporting the latter hypothesis includes our observation that the cells of some combined nevi display overlapping features with each other, making classification of the nevus components difficult.2Scolyer R.A. Zhuang L. Palmer A.A. Thompson J.F. McCarthy S.W. Combined naevus: a benign lesion frequently misdiagnosed both clinically and pathologically as melanoma.Pathology. 2004; 36: 419-427Crossref PubMed Scopus (48) Google Scholar Finally, genetic studies may shed further light on whether the epithelioid components of “so-called NFAEC” and DPN are indeed related, as their overlapping morphologic features appear to suggest.
Publication Year: 2007
Publication Date: 2007-05-01
Language: en
Type: letter
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 15
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