Welcome back to the journal review. This month we're working through the October twenty twenty-six issue of Dermatologic Surgery, and I've pulled four pieces that are worth your time — a confocal mapping technique for Mohs, a sobering look at how well preoperative imaging actually predicts depth of invasion, a SEER-based cancer risk study in extramammary Paget disease, and a reconstructive conundrum involving the upper lip and nasal sill. Let's get into it.

First up is a "How We Do It" piece out of the University of Bologna's oncologic dermatology unit, so this is a technique communication, not a study with results and limitations — think of it as a practical pearl you could adopt tomorrow. The problem they're solving is a familiar one if you use reflectance confocal microscopy for presurgical mapping: you get a beautiful en face view of atypical melanocytes or tumor nests under the confocal probe, but translating that image back onto the actual skin surface — correlating what you saw under the lens with where exactly that is on the patient — has always been the soft underbelly of noninvasive presurgical mapping. The authors' fix is refreshingly low-tech. They take the thin adhesive skin suture tapes you'd normally reach for after closing a wound, and instead use them as fiduciary markers during the confocal exam itself. They lay a piece of tape near the presumed tumor edge, image under confocal, and if they see residual atypia near that tape, they peel it up and reposition it further out, repeating this iterative process until the confocal view is clean at the tape's location. Because adhesive tape is a dense, sharply demarcated structure, it shows up unmistakably on the confocal image — unlike trying to eyeball a corresponding point on skin with no fixed landmark. Once they've walked the tape out to a tumor-free margin all the way around the lesion, they send the patient to the OR with the tape left in place, so the Mohs surgeon has a literal, physical outline of where to cut — no translation step, no guessing.

They explicitly compare this to the SMART technique — Superficial Margin Assessment with RCM Technology — described by Pellacani's group back in twenty eighteen for lentigo maligna mapping. SMART uses small incisions as fixed reference points, placed at set increments starting two millimeters beyond the clinical border, then progressively moved outward if melanoma features persist near a cut, with the final incisions doubling as the actual surgical margin and allowing direct histologic correlation to the exact imaged points. That histologic anchoring is SMART's real advantage — you know precisely what tissue corresponds to what confocal finding. But it comes at a cost: local anesthesia, multiple sequential incisions, more procedure time, and more trauma to the area before you've even started definitive excision. The tape method the Bologna group describes trades away that direct histologic correlation — you can't biopsy a piece of tape — but in exchange you get something noninvasive, fast to reposition, and easy on sensitive sites like the periauricular area shown in their case figure, where repeated incisions for mapping purposes are less appealing. The practical takeaway here is modest but real: if you already have confocal capability in your presurgical workflow, this is a nearly cost-free refinement — no new equipment, just a change in how you use tape you already stock — that could meaningfully cut down on wasted Mohs stages by giving the surgeon a more faithful starting map. It's not practice-changing in the sense of altering who gets confocal mapping, but for those who already do it, it's a genuinely useful workflow tweak worth stealing.

Next, a retrospective cohort study from Brigham and Women's Hospital asking a question that cuts right to the heart of surgical planning: when you order a CT or MRI before resecting an aggressive skin cancer because you're worried about deep invasion, how much should you actually trust that scan? The gap they're addressing is that despite imaging being routinely used to gauge local extension — whether a tumor has blown through the subcutaneous fat, or worse, invaded bone — nobody had rigorously quantified how often that imaging read actually matches what the pathologist finds on the final specimen.

Methodologically, this is a straightforward retrospective chart review across about two years at a single academic center, pulling every patient who had preoperative imaging specifically to evaluate for deep extension before resection. That design makes sense here — you're not manipulating anything prospectively, you're asking a diagnostic accuracy question against a fixed gold standard, which is exactly the kind of question a retrospective comparison of two already-collected data streams, imaging reports and pathology reports, is built for. The statistical tool doing the real work is a classic two-by-two diagnostic accuracy framework — sensitivity, specificity, positive predictive value, and negative predictive value — with histopathology serving as the reference standard. Worth pausing on what these actually mean in this context: sensitivity asks, of all the tumors that truly invaded beyond the fat on pathology, what fraction did imaging correctly flag; specificity asks the mirror question, of the tumors that did not extend that deep, what fraction did imaging correctly call negative. Positive predictive value then asks the question a surgeon actually cares about in the moment — if the radiologist says "beyond the fat," how often is that true — while negative predictive value asks whether you can trust a reassuring scan. These four numbers together, rather than a single overall accuracy figure, matter because a test can look impressive on sensitivity while being nearly useless on predictive value if the underlying prevalence of the finding is low, which turns out to be exactly the story here.

The cohort was thirty-nine patients, average age right around seventy-four, overwhelmingly cutaneous squamous cell carcinoma — about four in five cases — with the rest split between basal cell carcinoma, adnexal carcinoma, and a scattering of other histologies. Most imaging was CT, done mainly for head and neck tumors, which tracks with where surgeons get nervous about deep structures. Here's the headline: overall concordance between imaging and final pathology for invasion beyond the subcutaneous fat was only about sixty percent. And the discordance wasn't symmetric — imaging over-called deep invasion far more often than it missed it. In roughly a third of all cases, imaging suggested invasion beyond the fat that pathology did not confirm, while true misses — pathology finding deep invasion imaging didn't catch — happened in less than one in ten cases. Translating that into the accuracy framework, sensitivity and specificity were both mediocre, hovering in the mid-fifties to mid-sixties percent range, but the positive predictive value was the real eye-opener at only about thirty percent — meaning when the scan says "this has gone beyond the fat," it's wrong roughly seven times out of ten. The negative predictive value, by contrast, was quite good at around eighty-five percent, so a reassuring scan is reasonably trustworthy. Bone invasion specifically was a small subset — only five cases total — but even there, agreement was inconsistent, with misses running in both directions.

The authors are appropriately cautious in their discussion: this is a modest, single-institution, retrospective sample, selected specifically because these were patients worrisome enough to warrant imaging in the first place, so these findings describe imaging performance in a high-suspicion population, not a general screening population, and that selection almost certainly inflates the apparent false-positive problem to some degree. Still, the clinically meaningful signal — that imaging substantially overcalls deep invasion relative to final histology — held up as a dominant pattern rather than noise. For your practice, the actionable point is this: a positive preoperative scan suggesting invasion beyond the subcutaneous fat should raise concern and absolutely inform your surgical and reconstructive planning conversation with the patient, but it should not be treated as a foregone conclusion that will necessarily be confirmed on permanent sections — a meaningful fraction of these will turn out more limited than imaging suggested. A negative scan, on the other hand, is reasonably reassuring. This doesn't change whether you order imaging for high-risk CSCC and other aggressive tumors, but it should calibrate how much weight you put on a worrisome read when you're counseling patients preoperatively about the likely extent of surgery.

Third is a short communication using the SEER-seventeen registry to ask a focused epidemiologic question about extramammary Paget disease — specifically the minority of cases, something like a fifth to a quarter of all extramammary Paget disease, that arise outside the anogenital region, on extra-anogenital skin like the trunk or extremities. The clinical gap is straightforward: current guidelines for screening patients with extramammary Paget disease for associated internal malignancies are built entirely around the three classic anogenital primary sites — penoscrotal, perianal, and vulvar — and simply don't address what, if anything, you should be screening for when the disease shows up somewhere else entirely.

This is a registry-based retrospective cohort analysis, and the statistical workhorse is the standardized incidence ratio, or SIR, which is worth unpacking because it's a technique you'll see throughout cancer registry literature. The idea is indirect standardization: rather than comparing your patient cohort to some arbitrary control group you recruit yourself, you calculate how many cases of a given subsequent cancer you'd statistically expect to see in a general population matched to your cohort on age, sex, and calendar year of diagnosis, and then you compare that expected number to what you actually observed. An SIR of one means your cohort's risk matches the general population exactly; an SIR meaningfully above one means they're developing that cancer more often than you'd expect by chance alone, with the confidence interval telling you whether that elevation is statistically robust or could just be noise given small numbers. It's the right tool here because extramammary Paget disease is rare enough that you could never assemble a matched control cohort with adequate power, but the registry already contains population-level background rates to borrow from.

They identified four hundred ninety-two patients with extra-anogenital extramammary Paget disease, average age early seventies, with the large majority of lesions on the trunk and only a minority on the extremities or head and neck. To avoid surveillance bias — catching cancers that were already brewing and got picked up incidentally during the Paget disease workup — they excluded any second cancer diagnosed within the first two months. The standout finding: colorectal cancer was significantly elevated, with an SIR of about two and a third, meaning roughly double the expected rate, and this was the one statistically significant finding in the whole analysis. Critically, none of the genitourinary cancers traditionally linked to anogenital extramammary Paget disease — breast, bladder, kidney, ovarian, uterine, or prostate — showed any significant elevation in this extra-anogenital cohort; all of those confidence intervals comfortably crossed one.

The authors' conclusion is clinically practical and refreshingly specific: patients with extra-anogenital extramammary Paget disease appear to carry an elevated colorectal cancer risk and probably warrant colorectal screening attention, but there's no signal here to justify extending prostate-specific antigen testing, cystoscopy, or similar genitourinary surveillance to this population the way you would for anogenital disease. The honest limitations are worth naming — SEER doesn't capture high-risk histologic features like cytokeratin-20 positivity or depth of dermal invasion that current guidelines use to further stratify screening intensity, so this analysis can't tell you which extra-anogenital patients need more versus less vigilance. There's also always some misclassification risk with a cancer this rare, though restricting to histologically confirmed cases with explicit skin topography codes should minimize that. For your practice, this is a genuinely useful, actionable data point when you're coordinating surveillance for a patient with trunk or extremity Paget disease — it gives you a concrete, evidence-based answer to "should this patient get a colonoscopy," while reassuring you that you don't need to reflexively extend the full anogenital screening panel to a population where the data simply doesn't support it.

Last is a reconstructive conundrum, so this is a single case walkthrough built around a repair decision rather than a study with statistics — the value here is entirely in the reasoning. A sixty-nine-year-old woman had a small basal cell carcinoma just below the right nares cleared in a single Mohs stage, leaving a one-by-one centimeter defect that straddled two cosmetic subunits at once — the upper cutaneous lip and the nasal sill — and extended down to fascia. That subunit-straddling, full-thickness quality is exactly what makes these defects miserable: perinasal skin has little elasticity or subcutaneous padding to spare, and the free margins of both the nose and the lip are extremely easy to distort if you get the tension vectors wrong.

The authors walk through essentially the full differential of standard options and explain why each falls short for this specific defect. Linear closure risked asymmetry and functional compromise. A full-thickness skin graft risked a poor color and texture match with a contracted, depressed look. A rotation flap could hide its secondary defect in the nasolabial fold but would generate tension perpendicular to the rotation arc, risking unilateral lip asymmetry. Advancement flaps like an O-T, or rhombic flap options, would cross into other cosmetic subunits and reorient tension in unfavorable ways. A Mercedes flap looked appealing for horizontal closure without buckling, but its redistributed tension vectors risked tugging the nose downward. Even a two-stage interpolation flap, while reliable, meant more visits, more complex wound care, and a bigger scar for a defect the authors felt could be solved more simply. The non-negotiable constraint running through all of this was avoiding any stricture of the nasal sill, since that leads to alar collapse and compromised nasal airflow.

Their solution combined an advancement flap for the cutaneous upper lip component with a Burow's sling flap for the nasal sill component. The advancement flap handled the lip portion as a single-stage repair using similar hair-bearing skin, and with adequate undermining it covered real distance without excess tension. The clever part is what they did with the standing cutaneous cone that's generated superiorly, away from the defect, in the apical triangle — rather than simply excising and discarding that tissue, they elevated it on a pedicle of orbicularis oris muscle and used it as a vascularized sling flap to resurface the deep sill defect, reaching it with essentially no tension and no risk of columellar distortion. That's the generalizable teaching point: a standing cone you'd normally throw away can become a robust, muscle-pedicled local flap for resurfacing a second, deeper defect within the same wound. They're also explicit about the limits of this approach — for shallow sill defects, or ones extending medially onto the septum, granulation or grafting might actually be preferable alternatives, and they flag the standard rule that facial advancement flap length-to-width ratio shouldn't exceed three-to-one to protect flap viability. At six months, the patient had no airflow impairment, bilateral symmetry on smiling, good color and texture match, and scars that hid within the apical triangle, the inferior nasal margin, and an existing smoker's line — no revisions needed.

The practical takeaway for your own reconstructive decision-making is the broader principle, not just this specific flap combination: when you're closing a multi-subunit facial defect, look at your standing cutaneous cones not as waste tissue to be excised and discarded, but as a potential donor site for a vascularized sling to resurface an adjacent deficiency, particularly around the nasal sill where avoiding stricture is paramount. It's a nice example of getting two reconstructive problems solved with one incision pattern.

That wraps up this month's lineup — a tape-based confocal mapping trick worth adopting if you already use RCM, a useful reality check on how much to trust preoperative imaging before you counsel patients on extent of surgery, a registry study that gives you a concrete, defensible colorectal screening recommendation for extra-anogenital Paget disease, and an elegant two-flap solution for a classic perinasal reconstructive trap. Thanks for listening, and I'll see you next month.