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The lesions on this site share physical dimensions (i.e., they are all 1.5 mm or less in vertical dimensions) and, with possibly one exception, they either recurred locally, or metastasized. These characteristics were basic in my request in the 1970”s to the Tumor Registry. From a list of approximately 50 thin “melanomas,” there were 13 cases with either local recurrence, satellitosis (3cases), lymph node metastasis (9cases), or distant metastasis (4cases). From this group of 13 cases, the material on this site represents the cases for which slides were available in the 1970’s for review, and photography. Those slides are not currently available for review (I cannot find them). The material on this site represents photographic documentation that was created in late 1979, or early 1980. Six of the lesions measured less than 0.75 mm in vertical dimensions.
I tend to think of the common thin melanomas (i.e., lesions in the common premalignant dysplasia-melanoma sequence) as lesions showing both the pattern of the common final pathway in the epidermis, and a variant or typical vertical growth pattern in which rounded nests cluster in a widened papillary dermis (c16t3p1-3). There are exceptions, but in a study of this type I would have anticipated that most of the lesions would share this quality. My anticipations are fulfilled by only 2 of the lesions. To my surprise, there is a high component of “nevoid” MDM in this material. The thin nevoid melanomas in this collection have metastasized, or recurred locally. Some (at least 2) of the nevoid lesions have Spitz-like qualities. Several of the lesions, in histologic patterns, so closely resemble common nevi that they qualify as MDM, common nevus-like variants (c16t3P4 & 5 & c18t3P1-5). These nevus-like patterns are of the type that on pattern analysis might be misdiagnosed as a common nevus. One of the Spitz-like lesions did not metastasize, but did recur 38 months after the initial excision, and following regional perfusion. I suppose those observers, who seem to have trouble with the recognition of vertical growth patterns, might have classified this lesion as “atypical Spitz nevus.” This lesion was additionally distinguished by halo nevus-like phenomena. I suppose on this basis, the lesion might be characterized by some observers as Spitz nevus with halo nevus phenomena.
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