Welcome back to the journal review. This is your walkthrough of Dermatologic Surgery for February 2026, and we've got four pieces worth your time this month — a practical staining guide for a tricky sarcoma, two instructive case reports, and a small but provocative retrospective study that pushes back on a longstanding antibiotic recommendation. Let's get into it.

First up is a review-style technique article: "Dermatofibrosarcoma Protuberans on Mohs Frozen Sections: Tips, Pitfalls, and Mimickers When Using Hematoxylin and Eosin Staining and CD34 Immunostaining for Intraoperative Frozen Section Margin Assessment." This isn't an original study with a cohort and outcomes — it's a practical, image-driven guide aimed squarely at Mohs surgeons and their lab staff who are trying to read DFSP margins in real time, and it earns its place because there really isn't a concise summary of these staining pitfalls written specifically for our workflow.

The setup is familiar territory: DFSP on hematoxylin and eosin is a poorly circumscribed proliferation of bland, monotonous spindle cells arranged in short fascicles or a storiform pattern, classically infiltrating subcutaneous fat in that honeycomb pattern with entrapped adipocytes and notably little inflammation or fat necrosis — which is your first clue distinguishing it from an inflammatory process or a dermatofibroma. CD34 immunostaining is positive in the great majority of cases, cited here as somewhere in the ninety to one-hundred percent range, and it's a valuable adjunct for confirming margins. But — and this is the whole point of the article — CD34 is not a clean binary, and the piece walks through where it fools you in both directions.

On the H&E side, the authors flag several mimickers you'll actually encounter. Adipose tissue can look artifactually more cellular on frozen section and mimic DFSP's fat infiltration, especially soon after a recent biopsy when reactive spindle cells are trickling between adipocytes — and CD34 doesn't bail you out here because it also stains the normal dendritic cells and small vessels within fat, so positivity alone doesn't prove tumor. Atrophic skeletal muscle can look like crunched-together multinucleated cells mimicking giant cell fibroblastoma, the pediatric DFSP variant, and myxoid DFSP in adults can likewise show multinucleated cells that echo that pattern. Prior use of porcine gelatin hemostatic sponge at a biopsy site produces a vacuolated, cellular appearance from reactive myofibroblasts and histiocytes engulfing sponge fragments, closely mimicking the honeycomb look of DFSP in fat — the tell here is recognizing the purple arabesque sponge fragments at higher power, and the fact that these reactive cells are typically CD34 negative or only patchy. And a purely technical pitfall: sections cut too thick will look falsely hypercellular; rotating the fine focus to reveal overlapping nuclei in different focal planes tells you the section is thick, and recutting thinner usually resolves it.

On the CD34 side, the key teaching point is understanding background staining in normal skin so you don't over-call it. Normal dermis is loaded with CD34-positive dendritic cells, and staining is enhanced around adnexal structures, eccrine coils, vessels, and nerves — all of which can mimic DFSP if you don't know the baseline. The useful discriminator is that scar and granulation tissue myofibroblasts are usually CD34 negative, even though the endothelial cells lining vessels within that scar will still light up. Fat necrosis histiocytes are typically patchy or negative too. So CD34 is best deployed specifically to separate DFSP from postsurgical reactive change or scar, not as a freestanding diagnostic test in isolation. The article also notes real variability between frozen and permanent tissue — one cited report found CD34 negative on formalin-fixed tissue but positive on frozen sections, and another found increased dermal CD34 staining specifically on frozen sections — and warns that fibrosarcomatous DFSP, the more aggressive variant, may show diminished or absent CD34 expression altogether, which is exactly when you're most tempted to rely on the stain and exactly when it may let you down. Practically, they recommend checking your internal positive controls every time — normal dermis and periadnexal spindle cells should show some staining, and if they don't, repeat the stain rather than trusting a falsely reassuring negative.

For the practicing Mohs surgeon, this is genuinely useful bench-side reference material rather than practice-changing data, since there's no outcomes claim here — but it's the kind of practical takeaway you want in your back pocket the next time a DFSP re-excision or recurrence case comes through and the spindle cells in the fat aren't behaving the way you expect.

Next, a case report: "Herpes Zoster Developing Within Mohs Micrographic Surgery Scar." A 92-year-old woman with Fitzpatrick skin type three had Mohs surgery for an acantholytic squamous cell carcinoma of the jawline, cleared in two stages with a flap repair. Ten months later, a small new squamous cell carcinoma appeared anterior to that scar and was again cleared with Mohs, healing uneventfully. Three months after that second surgery, she came in with erythema, swelling, and tenderness around the jawline scar, and exam showed an indurated subcutaneous nodule right in the surgical field — understandably raising concern for tumor recurrence. A biopsy and CT scan were ordered. Within days, she developed painful crusted papules across the scalp, cheek, and jawline in a clear dermatomal distribution, and the biopsy confirmed varicella zoster virus — positive VZV stain, negative herpes simplex virus one and two, with acantholytic cells and intranuclear inclusions on histology and only mild inflammation. The CT scan was normal, no residual carcinoma was found on deeper sections, and she was treated with high-dose oral acyclovir with full resolution — notably, she'd received the shingles vaccine back in 2015, underscoring that vaccination doesn't guarantee prevention.

The discussion situates this against prior case reports of zoster arising in surgical scars, all of which described typical grouped vesicular lesions appearing early, within about two weeks of surgery. This case breaks that pattern on two fronts: the eruption occurred more than three months postoperatively, well after the expected surgical inflammatory window had settled, and the initial presentation was an atypical indurated nodule rather than classic vesicles — clinically indistinguishable from tumor recurrence — with the more recognizable dermatomal vesicular eruption only following days later.

The practical takeaway here is purely a pattern-recognition pearl, not a change in your standard workup: when a new nodule appears in or near a Mohs scar months out from surgery, don't let recency of surgery bias you away from considering zoster, especially in older or possibly immunosenescent patients, before or alongside your recurrence workup. Early recognition matters because early antiviral therapy shortens the course and reduces postherpetic neuralgia risk.

Third is another case report: "Squamous Cell Carcinoma Arising in Extragenital Lichen Sclerosus et Atrophicus in a Fitzpatrick Type Six Patient." Lichen sclerosus et atrophicus classically involves the anogenital area in postmenopausal women, and extragenital disease without any genital involvement is genuinely rare — cited here at around six percent of cases — most often turning up on the neck, shoulders, or upper trunk, with a known risk of malignant transformation to squamous cell carcinoma. This report is notable for two overlapping rarities: a facial, specifically cheek, location, and occurrence in a Fitzpatrick type six patient, a population essentially undocumented in the extragenital LSA literature.

The patient was a 68-year-old woman with a year-long swollen, itchy, sometimes painful eruption on the left cheek, which she reported began at the site of a chemical burn she'd sustained roughly a decade earlier — she'd also noticed eyelid drooping from the swelling and formication in the area, and topical steroids from an outside dermatologist hadn't helped. Exam showed a well-circumscribed ivory-white atrophic plaque with hyperkeratotic, erythematous debris at its superior edge. Biopsy showed the classic LSA triad of epidermal atrophy with hyperkeratosis, hydropic change at the dermoepidermal junction, and papillary dermal hyalinization with a lymphocytic infiltrate — but also a focus of atypical keratinocytes infiltrating between collagen bundles, which stained positive for p63, confirming squamous cell carcinoma arising within the LSA. She underwent Mohs surgery, cleared in two stages, with complex multidisciplinary reconstruction involving a cheek advancement flap, a free superficial inferior epigastric artery flap for midface reconstruction, and an abdominal wall advancement flap for the donor site.

The discussion's key clinical reasoning is that the prior chemical burn likely acted as the koebnerizing trigger for localized extragenital LSA, consistent with prior reports of LSA arising at sites of radiation or scarring — trauma as a plausible driver of this entity outside its usual genital distribution. The authors also make a point of noting that the combination of an unusual location and darker skin phenotype likely contributed to a delayed diagnosis, given that LSA is classically described and recognized in lighter-skinned, postmenopausal women. There's no cohort data here, no defined malignant transformation rate calculated from this case — the citation of three-and-a-half to five percent transformation risk is background literature, not a new finding — so the discussion is appropriately framed as raising awareness rather than establishing new risk figures.

The practical takeaway is a diagnostic vigilance point: keep extragenital LSA, and its malignant potential, on your differential for atrophic, sclerotic plaques at sites of prior trauma or burns regardless of skin type or body location, since this population may be underrepresented and therefore under-recognized in practice.

Last is an original retrospective study: "The Rate of Infection Following Mohs Surgery of the Groin." The clinical gap here is sharply defined — the 2008 advisory statement on prophylactic antibiotics in dermatologic surgery, which many of us still practice by, recommends antibiotics for groin Mohs cases based on a cited ten percent infection rate. But that figure traces back to a single-center descriptive study of only ten total cases — about as thin an evidence base as you can have for a recommendation that shapes real prescribing behavior.

To address this, the authors did an IRB-approved retrospective chart review from two Mohs surgeons at the University of Rochester, covering January 2017 through December 2024, capturing all adults undergoing Mohs surgery of the groin, which they defined broadly to include genitalia and inguinal folds. This retrospective design makes sense here — the authors don't spell out the rationale explicitly, but groin Mohs is uncommon enough at any single center that a prospective trial with meaningful power would take many years, so pulling everything from an eight-year chart window is really the only feasible way to accumulate even a modest series. They collected the usual risk-factor variables — age, body mass index, smoking, diabetes, immunosuppression — along with tumor type, location, stage count, defect size, antibiotic use, and surgical site infection within thirty days, using a fairly inclusive infection definition of either clinical suspicion alone or clinical suspicion plus a positive culture.

They identified 27 cases total. Most patients were men, and the tumor spread across squamous cell carcinoma as the clear majority, with smaller numbers of basal cell carcinoma and extramammary Paget disease. Anatomic sites were mostly penile, followed by inguinal folds, labia, and scrotum. About one in five patients were active smokers, about one in five had diabetes, and roughly one in ten were immunosuppressed. The headline finding: zero surgical site infections across all 27 cases — and notably, not a single patient received prophylactic antibiotics.

The authors are appropriately cautious in how they frame this. A zero percent infection rate in a series this size doesn't statistically rule out a true underlying risk anywhere near the ten percent figure that guidelines currently cite — with only 27 cases, the confidence interval around a zero-event finding is genuinely wide, so this is more of a signal than a definitive rebuttal. They also flag real limitations in subgroup analysis: only three uncircumcised patients underwent penile Mohs, so any comparison of infection risk by circumcision status is essentially uninterpretable here, and only three patients were immunosuppressed, which is too few to say anything meaningful about that population's risk. It's a single-center, retrospective design with no comparator arm of antibiotic-treated patients, so this can't formally test whether antibiotics change outcomes — it only describes what happened when they weren't used.

Here's where I'd draw the line between interesting and practice-changing. This is not yet practice-changing in the sense of a guideline update — the sample is too small and the design too limited to overturn the 2008 advisory statement outright. But it is a meaningful, practical data point that should make you comfortable individualizing your approach: in a series of nearly thirty groin Mohs cases with essentially routine demographics and no prophylactic antibiotics at all, there wasn't a single infection. Combined with the fact that the original ten percent figure rests on just ten cases from one older study, this gives you legitimate grounds to reconsider routine antibiotic prophylaxis for groin Mohs in average-risk patients, while still using clinical judgment — and probably erring toward antibiotics on a case-by-case basis — for your immunosuppressed or otherwise higher-risk patients, where this dataset simply can't guide you.

That wraps our four articles for this February issue — a hands-on staining reference for DFSP margins, two sharp case reports on atypical zoster and skin-of-color LSA transformation, and a small but well-aimed challenge to a decades-old antibiotic recommendation for groin surgery. Thanks for listening, and we'll see you next month.