Verhoeff-van Gieson May Distinguish Desmoplastic Melanoma From Re-Excision Scar.

Desmoplastic melanoma (DM) remains a challenging diagnosis. Because DM can resemble a scar on histopathology, evaluation of re-excision specimens may be particularly difficult due to the need to distinguish residual DM from scar tissue formed during the initial biopsy, especially in markedly regressed or traumatized lesions. Although several immunohistochemical stains, including S100 and SOX10, have high sensitivity for DM, these stains are also positive in re-excision scars. Verhoeff-van Gieson (EVG) is a special stain that visualizes elastin fibers, but no studies to date have used EVG to compare the distribution of elastin in DM with that of scar tissue. We stained 17 DMs and 17 re-excision scars with EVG and found that 76% (13/17) of DMs demonstrated preservation of elastic fibers between melanocytes, while elastin was absent in 100% of scars. Two DMs, while negative for intratumoral elastin, showed layering of elastin at the base of the lesion. Another 2 DM specimens, from 88- and 92-year-old patients, respectively, were entirely devoid of elastin, perhaps due in part to natural age-related degenerative changes. In DMs that retain elastin between melanocytes, EVG may be useful in differentiating DM from scar. Caution should be exerted when specimens are negative for intratumoral elastin, particularly in older patients and when excision is significantly delayed, as regeneration of elastin fibers has previously been shown to begin 3 months after biopsy.