Welcome back to the journal review. This is the April twenty twenty-six issue of Dermatologic Surgery, and we've got four communications worth walking through today — a UV physics study on window tints, a SEER database analysis on Merkel cell carcinoma, a single-center outcomes study on dermatofibrosarcoma protuberans, and a case report on using CD34 immunostaining intraoperatively for a superficial angiomyxoma. Let's get into it.

First up is an original comparative study, though a small and pragmatic one, looking at UV rejection in window tints — professional-grade versus e-commerce. The background here is one you've probably filed away somewhere: there's a well-documented left-side predominance of skin cancer in drivers from ultraviolet exposure through the car window, and there's actually a nice epidemiologic hint that patients with right-sided nonmelanoma skin cancer are far more likely to have window tints installed than those with left-sided disease. So tints clearly matter for photoprotection, but unlike sunscreen, there's no SPF-equivalent standard, and dermatology guidance has largely stuck to recommending professional-grade products without addressing whether the cheaper e-commerce options people actually buy are any good.

Methodologically, this is a bench study, not a clinical one. The authors gathered twenty-one professional-grade tints from two major manufacturers and ten best-selling tints from Amazon, all advertised as blocking more than ninety-nine percent of UV, and ran them through a solar simulator with a calibrated radiometer measuring UVA and UVB transmittance before and after tinting, three trials each. Why bench testing rather than, say, a clinical outcomes study? It's simply the only way to isolate the actual optical performance of the product itself, stripped of behavioral confounders like inconsistent application — the same logic that governs in vitro SPF testing. They picked the Amazon products using incognito browsing and a VPN specifically to avoid personalized search results skewing which products got selected, which is a nice touch of methodological hygiene for a study like this.

The results are the whole point. Professional-grade tints performed close to their claims — average UVA rejection around ninety-nine and a half percent, though about one in five still technically fell short of the advertised ninety-nine percent threshold. UVB rejection was essentially uniform and excellent across the board for professional tints. The e-commerce tints told a different story: average UVA rejection dropped to the mid-nineties, and seven out of ten fell short of their own ninety-nine percent claim, with one outlier rejecting only about two-thirds of UVA — a genuinely poor result for a product marketed as near-total UV protection. UVB performance among the Amazon tints was better but still inconsistent, with that same outlier underperforming there too. The difference between the two groups was statistically significant for both UVA and UVB, and here the significance actually tracks with something clinically real — a tint that blocks two-thirds of UVA instead of ninety-nine percent is not offering the protection your patient thinks they're getting.

Limitations are honestly stated: small sample of e-commerce tints, a single time-point snapshot of a "best-sellers" list that will drift over time, and no assessment of batch-to-batch variability since only one unit per product was tested. So take the specific percentages as a signal, not a definitive catalog.

Practically, this isn't practice-changing in the sense of a new algorithm, but it is a nice piece of ammunition for patient counseling — when patients ask about tinting their car windows for photoprotection, you can now say that professional installation is worth the premium, and that the cheapest bestseller on Amazon claiming ninety-nine percent UV blockage may not deliver anywhere close to that. It also reinforces the broader point that this field badly needs an SPF-style standardized UV rejection rating for tints, which right now doesn't exist.

Next, a database-driven original study on Merkel cell carcinoma and the effect of prior malignancies on survival — a nice complement to the same group's earlier finding that malignancies arising after a Merkel diagnosis worsen survival. The open question here was the mirror image: does having a cancer history before your Merkel diagnosis change how that Merkel behaves, or does it just add general mortality risk without making the Merkel itself more aggressive?

They used SEER-17 data from two thousand to twenty twenty-one, pulling out microscopically confirmed Merkel cases and splitting them by presence or absence of a prior malignancy. This is the obvious design choice for a rare tumor like Merkel — you simply cannot power a prospective study around this question, so a large national registry is the only realistic vehicle, even though it comes with the usual SEER trade-offs of no comorbidity or treatment granularity. They used competing-risks Fine-Gray modeling for Merkel-specific survival — appropriate given that these are older patients with real competing mortality from other causes — and standard Cox modeling for overall survival, adjusting for the expected demographic and tumor-stage confounders.

The topline finding is genuinely useful for risk stratification: having any prior malignancy did not worsen Merkel-specific survival in aggregate, but it did significantly reduce overall survival — which makes intuitive sense, since a cancer-experienced patient population simply carries more competing mortality risk. The more clinically interesting finding is in the subtype breakdown. A prior history of chronic lymphocytic leukemia significantly worsened both Merkel-specific survival and overall survival, and non-Hodgkin lymphoma showed the same pattern for overall survival with a trend toward worse Merkel-specific survival that didn't quite cross significance. In contrast, prior solid organ malignancies — breast, colorectal, kidney, lung, prostate, bladder — did not worsen Merkel-specific survival at all, though colorectal and lung cancer histories were associated with worse overall survival, presumably just reflecting the burden of those diseases themselves rather than any interaction with the Merkel tumor.

The biological read the authors offer is that CLL's immunosuppressive effects likely blunt the immune response needed to control a famously immunogenic tumor like Merkel, whereas a solid organ cancer history doesn't functionally compromise that immune surveillance in the same way. Limitations are the standard SEER issues — no comorbidity data, no treatment detail, so residual confounding is possible.

The practical takeaway here is fairly targeted: this doesn't change your surgical approach to Merkel cell carcinoma, but it is a genuinely useful piece of risk stratification for the multidisciplinary conversation. A Merkel patient with a CLL history should probably be flagged as higher risk and discussed more assertively with medical oncology, whereas a prior solid organ cancer alone shouldn't be treated as a marker of a more aggressive Merkel course.

Third, a retrospective single-center study on dermatofibrosarcoma protuberans, comparing outcomes by treatment modality. The background gap they're addressing is a familiar one in the DFSP literature — everyone agrees Mohs or other margin-controlled techniques, referred to here under the umbrella of peripheral and deep en-face margin assessment, or PDEMA, outperform standard wide excision, but the authors note that long-term outcome data tying treatment type to actual recurrence and survival remain sparse.

This is a retrospective chart review spanning twenty-one years at a single academic center, one hundred thirty-three patients total, which is really the only feasible design for a tumor this rare — you're not going to randomize DFSP patients to Mohs versus wide excision, so a long look-back at a large referral population is the pragmatic substitute, with the understood tradeoff of incomplete follow-up data inherent to retrospective EMR review.

The results are quite clean. About seven in ten patients in this cohort were treated with standard excision without complete margin assessment, reflecting that this remains the more commonly used approach in practice despite guideline preference for margin-controlled surgery. Tumors selected for PDEMA were significantly smaller preoperatively, and their postoperative defects were also significantly smaller — meaning even accounting for selection toward smaller lesions, PDEMA was more tissue-sparing. Positive margin rates were actually similar between the two groups, with no significant difference — five PDEMA patients still didn't achieve complete clearance. But despite equivalent margin-positivity rates, local recurrence was dramatically different: zero recurrences in the PDEMA group compared with about sixteen percent in the standard excision group, a difference that was statistically significant and clearly clinically meaningful. Within the standard excision group, using a margin of two centimeters or more roughly halved the recurrence rate compared to narrower margins, though that particular comparison didn't reach statistical significance — likely, as the authors note, simply an underpowered subgroup. Importantly, treatment modality did not translate into a difference in disease-specific or all-cause mortality, consistent with the generally indolent biology of DFSP even when it recurs locally.

The authors' interpretation is that margin-assessed surgery's recurrence advantage isn't just about achieving negative margins on paper — since positivity rates were statistically similar between groups — but likely reflects something about the completeness and precision of that clearance that isn't fully captured by a binary positive-versus-negative margin call. They's transparent about limitations: small subgroup sizes for the more granular comparisons, inconsistent follow-up typical of retrospective referral-center data, and a caution against over-reading p-values in underpowered strata.

Practically, none of this should surprise you or change what you're already doing — margin-controlled surgery remains standard of care for DFSP, and this adds one more concordant single-center data point with a striking zero percent recurrence rate in the PDEMA arm. The more useful nugget for daily practice is the reminder that when PDEMA truly isn't available and you're stuck with standard excision, pushing for a two-centimeter margin rather than something narrower is worth the extra tissue given the halved recurrence signal, even though it didn't reach significance here.

Last, a case report — a technique-flavored one — on using CD34 immunostaining intraoperatively during Mohs surgery for a superficial angiomyxoma. Quick framing: these are rare, indolent but locally destructive tumors with a substantial reported recurrence rate of twenty to thirty percent after standard excision, and the diagnostic and treatment challenge is that their myxoid stroma can be genuinely difficult to distinguish from ordinary solar elastosis under the microscope, which is very plausibly why standard excision recurrence rates are so high.

The case is a healthy man in his sixties with a superficial angiomyxoma of the left nasal ala present for nine years. Before committing to CD34 as an intraoperative tool, the authors first confirmed CD34 positivity on the original diagnostic biopsy — which they explicitly flag as a necessary prerequisite, since only about seventy percent of these tumors actually stain positive for CD34. They also worked up the patient for Carney complex given the anatomic location, including an echocardiogram to exclude a cardiac myxoma, which came back unremarkable. During Mohs, they used CD34 on the debulking layer and subsequent frozen sections, with a same-session control biopsy from adjacent normal cheek skin to establish the baseline staining pattern of native dermal vasculature — a smart control given that CD34 also stains normal endothelium, so you need a comparator to know what "background" looks like versus tumor stroma. Clearance was achieved in a single stage down to the perichondrium, and the defect was closed with a bilobed transposition flap.

The teaching point is straightforward and useful: CD34 highlights the stromal spindle cells and small vessels of superficial angiomyxoma well enough in the superficial dermis to help distinguish tumor from solar elastosis — which is likely the exact ambiguity driving high recurrence after excision without this kind of margin clarity. The authors note the stain is less reliable at the deep margin because of heavy, variable background staining there, so its greatest value is peripherally, not deep. This is only the fourth reported use of Mohs for this tumor and, as far as they note, the first to use intraoperative immunostaining rather than confirming the diagnosis on biopsy alone and proceeding with routine hematoxylin and eosin during surgery. There's also a small practical aside about insurance: in this case, the Mohs procedure itself was covered, but the immunostains billed separately were denied — worth knowing as you counsel patients and code accordingly, though they caution this will vary by payer and state.

For your practice, this is a nice technical pearl rather than anything practice-changing on its own given it's a single case — but it's a low-friction addition to your existing IHC-in-Mohs toolkit. If you're already comfortable using CD34 for dermatofibrosarcoma protuberans or other spindle cell tumors, extending it to superficial angiomyxoma, with pre-confirmation of positivity on the original biopsy and a same-day normal-skin control, is a reasonable and well-justified way to sharpen your margins on a tumor that otherwise recurs at meaningfully high rates after standard excision.

That wraps up this month's four communications — a reminder that patient-facing photoprotection counseling extends beyond sunscreen into the tint on their windshield, that prior CLL history deserves a second look when you're staging and discussing a Merkel cell patient, that margin-controlled surgery keeps earning its keep in DFSP even when positive-margin rates look similar on paper, and that your immunohistochemistry toolkit for Mohs can reasonably stretch to rare myxoid tumors like superficial angiomyxoma when the biopsy supports it. Thanks for listening, and I'll see you next month.