Figure 1-Low power magnification of the scar taken from the lip. The previous biopsy showed a hypertrophic actinic keratosis that extended to the shave margins. This prior original biopsy showed no atypical melanocytic proliferation
Figure 4-Higher power magnification of the S100 positive cells and the negative staining of the hemosiderin-laden macrophages.
Issues in Dermatopathology
Dermatology and pathology residents are taught early on in their training, "Beware the diagnosis of a scar in sun-damaged skin!"
A recent case illustrated the pitfalls of relying solely upon immunohistochemical stains for a diagnosis. Figures 1 and 2 depicted a scar, produced from a previous shave biopsy of a hyperkeratotic lesion from the lip. The original diagnosis was a hyperplastic actinic keratosis that extended to the surgical shave margins. No atypical melanocytic proliferation was present in any of the biopsies. An S100 stain highlighted numerous spindle cells in the re-excision specimen. An analysis of the spindle cells showed a bland cytology and no melanin pigmentation. Correlating the current findings with the previous biopsy, the histopathologic diagnosis was most consistent with a scar with S100 positive staining cells.
Of course, the traditional histopathologic criteria to aid in the differential diagnosis of a scar versus a desmoplastic melanoma still applies. Desmoplastic melanomas usually exhibit hyperchromatic spindle cells embedded within a myxoid background. Occasional mitotic figures may be present associated with a patchy chronic inflammatory cell infiltrate. The dermal-epidermal junction may exhibit atypical melanocytes. All of these features were lacking in our current cases.
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Last Updated June 10, 2005
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