Welcome back to the journal review. This is the May 2026 issue of JAMA Dermatology, and we've got a single piece to dig into today from the Images in Dermatology section — a case report titled "Melanoma Arising in a BAP1-Inactivated Melanocytic Tumor," from a group including Ashfaq Marghoob at Memorial Sloan Kettering. Given our audience, this is a short one, but it's dense with practical surveillance implications, so let's take our time with it.

This is a case report, so no methods section to dissect and no statistical results to translate — the value here is entirely in the clinical pearl and the teaching point. Let me walk you through the presentation.

The patient is a woman in her thirties with a known germline BAP1 variant and a striking phenotype — over two hundred melanocytic nevi, most of them sessile to dome-shaped, the kind of morphology that on gross exam just reads as garden-variety intradermal nevi. She's on total-body photography surveillance, which is exactly the right infrastructure for someone with this nevus burden and this genotype, because the whole game with BAP1-inactivated melanocytic tumors — BIMTs — is detecting subtle interval change against a baseline, not picking the "ugly duckling" out of a field of visually similar lesions.

On this visit, one dome-shaped chest lesion had changed from baseline. The original BIMT was still identifiable — eccentric globular pattern, which is one of the described dermoscopic signatures for these tumors — but now there was asymmetric enlargement within a portion of the lesion showing polymorphous vessels, shiny white lines, a negative network, and peripheral globules. If you strip away the BAP1 context, that's just a straightforward dermoscopic melanoma pattern. The excisional biopsy confirmed melanoma, thin — point four millimeters — arising in direct association with the BIMT. Re-excision was done with one-centimeter margins, appropriate for that Breslow depth, and she's been recurrence-free at three years.

Now, the discussion is really where this case earns its keep, and it functions almost like a mini-review of BAP1 tumor predisposition syndrome for the practicing dermatologic oncologist. A few points worth anchoring on. First, the histologic and molecular architecture of BIMTs: a biphasic dermal population of bland nevomelanocytes admixed with large epithelioid cells that have lost nuclear BAP1 staining, driven by a two-hit combination — a mitogenic driver, usually a BRAF variant, plus BAP1 loss of function. Second, the dermoscopic taxonomy — the authors cite five described patterns, ranging from structureless pink-to-tan backgrounds with irregular globules or peripheral vessels, to a network with raised structureless pink-to-tan zones, to a purely globular pattern. The clinical takeaway from that taxonomy is that these lesions have a recognizable, reasonably consistent dermoscopic signature that's worth pattern-training your eye on, precisely because they're so easy to dismiss as banal papules on gross morphology alone.

Third — and this is the systemic disease point that matters most for your practice — multiple BIMTs should trigger suspicion for an underlying germline BAP1 variant, and dermatologists are often the first clinician to spot the cutaneous clue that sets genetic counseling and testing in motion. Once a germline variant is confirmed, the surveillance cascade is substantial: annual ophthalmologic exams for uveal melanoma starting at sixteen to eighteen years of age, and annual renal imaging — MRI preferred, ultrasound as a fallback — beginning at age thirty, because up to eighty-five percent of germline carriers develop at least one BAP1-associated tumor over a lifetime, with penetrance approaching essentially universal. Cutaneous melanoma itself shows up in roughly one in eight to one in four of these variant carriers, which is why skin surveillance starting at eighteen to twenty years old, done annually or twice yearly, is part of the recommended protocol. Importantly, the guidance is explicit that routine excision of BIMTs is not recommended — biopsy is reserved for lesions with suspicious clinical or dermoscopic features, or those showing documented change on serial imaging, which is exactly the scenario that played out in this case.

The genuinely novel contribution here, and the authors are appropriately measured about it, is the question of whether BIMTs themselves can serve as direct melanoma precursors — not just markers of syndromic risk, but lesions that can transform. The literature on this is described as a handful of isolated case reports, so this is a hypothesis-generating single observation, not established biology. There's no denominator, no incidence estimate, nothing that lets you quantify transformation risk for a given BIMT. That's the honest limitation of a case report — n of one, no control for how many stable BIMTs this patient's clinic has followed without event, and no way to know if this is a rare stochastic event or a meaningfully elevated risk specific to BIMTs as a lesion class.

So what do you actually do with this. The practice-changing element isn't really practice-changing so much as practice-reinforcing: total-body photography and sequential dermoscopic monitoring in patients with high BIMT burden or confirmed germline BAP1 variants is the correct standard of care, and this case is a clean illustration of that surveillance strategy working exactly as intended — catching a thin melanoma at point four millimeters through interval change rather than through morphology alone. The genuinely new idea — that BIMTs may be direct melanoma precursors rather than purely syndromic markers — is interesting but not yet actionable in the sense of changing your excision threshold; the existing guidance to biopsy only for suspicious change, not routine excision, still stands. What this case should sharpen is your index of suspicion and your dermoscopic vigilance specifically within lesions you've already flagged as BIMTs on baseline imaging, and it reinforces referral for genetic counseling whenever you encounter a patient with multiple lesions fitting this phenotype.

That wraps our coverage for this episode. Thanks for listening, and we'll see you next month.