25 Apr 1996
I've just ordered my third S-100 on an obvious dermatofibroma in as many days. I don't know why I am afflicted by the bouts of paranoia that I may be missing a desmoplastic melanoma. Perhaps it is because every derm path CME lecturer I have ever heard makes it a point to gleefully show some incredibly bland-appearing spindle cell lesion that some hayseed shlump like me out in the hinterlands called benign, but then metastasized to every organ, from adrenals to zygoma, and killed the patient. Maybe it's because every desmoplastic melanoma I see is more bland than the one before it.
Anyway, here's my SOP: if I have a strictly spindle cell lesion of the dermis that looks like a dermatofibroma but does _not_ have any evidence of epidermal hyperplasia or hyperkeratosis over it, or does not have a grenz zone, then I usually order an S-100. I used to skip the S-100 if there was no evidence of a junctional melanocytic component over the lesion, but then one of my partners showed me a case where there was only a minimal junctional component that was picked up only in subsequent levels, and the S-100 was strongly positive. Then I had to throw that criterion out the window.
I feel like I am overutilizing the S-100, but the downside of missing a melanoma is so great, I feel like I have no choice.
I would be interested to know how others handle these cases. Please e-mail me with your thoughts on this.