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Welcome back, DERM Community.
Last issue we covered alopecia in women, walking through female pattern hair loss and the workup it deserves but rarely gets (and you loved it!).
This week we're looking at a lesion that gets the opposite problem: too much confidence, not too little.
Everyone in primary care has probably seen a seborrheic keratosis. Most clinicians diagnose it on sight, in under three seconds, without a second look. That speed is earned in the overwhelming majority of cases. It is also exactly how melanoma gets missed.
A patient has a "stuck-on," waxy, brown papule on the upper back. It's been there for years, and it looks like a dozen others nearby.
The clinician glances at it, says "that's just a seborrheic keratosis," and moves on. Eighteen months later the same lesion has changed shape, and the biopsy comes back as melanoma.
Seborrheic keratosis is common enough to be nearly ubiquitous in patients over 40, and that ubiquity is precisely what erodes vigilance around it.
Five habits keep this lesion under-examined
1. Diagnosing on sight alone
Calling SK by gestalt, without dermoscopy, has a real failure rate: some SKs get misdiagnosed as skin cancer, and some melanomas get waved off as SK. Dermoscopy meaningfully improves accuracy for clinicians at every experience level. The fix: dermoscope every pigmented lesion before naming it. Milia-like cysts and comedo-like openings support SK. A blue-white veil, atypical network, or irregular streaks means biopsy, not reassurance.
2. Treating "irritated SK" as a final answer
Irritation from clothing or scratching is often the real cause, but the dermoscopic features of irritation overlap with features seen in melanoma hiding inside an SK. If a lesion doesn't improve once the trigger is removed, or it's tender, ulcerated, or friable, it needs tissue sampling, not just the label "irritated."
3. Removing SKs without deciding on a pathology plan first
Many practitioners shave or curette SKs for cosmetic reasons without sending anything to pathology. That's fine for a lesion with a long stable history and clean dermoscopic features. Anything atypical, recently changed, or ambiguous should get a shave biopsy instead of just being discarded.
4. Undertreating dermatosis papulosa nigra (DPN)
This facial variant of SK, common in patients with darker skin, is often dismissed as cosmetic or treated with techniques that risk hypopigmentation or hyperpigmentation. The biology is the same as SK elsewhere. The fix is gentler technique (light electrodesiccation, fine scissor excision, lower-intensity cryotherapy) plus upfront counseling on dyspigmentation risk, not declining to treat at all.
5. Mismanaging concern about sudden SK eruptions (sign of Leser-Trélat)
A large cohort study found no solid evidence linking eruptive SKs to internal cancer risk, though case reports of the association (mostly adenocarcinomas) persist. Gradual accumulation of SKs over years needs no workup. A genuinely abrupt eruption over days to weeks, especially with pruritus or acanthosis nigricans, does warrant an age-appropriate cancer screen.
Why this matters
Seborrheic keratosis is one of the highest-volume diagnoses in dermatology and primary care combined, and its very familiarity is what makes it a soft target for both overtreatment and underinvestigation.
Reflexive removals without pathology waste visits and specimens on lesions that were never going to be informative, while reflexive reassurance on lesions that deserved a second look is how SK-like melanoma gets its head start.
The stakes aren't symmetric.
A missed SK-like melanoma has a real cost in delayed diagnosis. An unnecessarily biopsied benign SK has a real but much smaller cost in time and money.
That asymmetry is the argument for keeping the threshold to look closer, dermoscope, biopsy, refer, low, even on a lesion you're confident about.
Your practical reset
Dermoscope before you name it. Milia-like cysts and comedo-like openings confirm SK. Blue-white veil, atypical network, or irregular streaks mean biopsy, not reassurance.
Don't let "irritated" close the differential. If it doesn't settle once the trigger is removed, or it's tender, ulcerated, or friable, it needs tissue.
Decide the pathology plan before you treat. Classic, stable, dermoscopically clean lesions can be destroyed without a send-out. Anything atypical or changed gets a shave biopsy.
Treat DPN as a real request, not a cosmetic afterthought. Offer gentler technique and counsel on dyspigmentation risk rather than declining to treat.
Match your workup to the eruption, not the sign's reputation. Gradual accumulation needs nothing. A genuinely abrupt crop, especially with pruritus or acanthosis nigricans, warrants an age-appropriate malignancy screen.
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👋🏻 Thank you for being here, DERM community!
Seborrheic keratosis earns its reputation as the safest diagnosis in dermatology, and that reputation is exactly why it deserves a second look more often than it gets one. The lesion is almost always benign. "Almost" is the word that matters.
Dermoscope before you name it, keep a pathology plan for anything you remove, and don't let a familiar-looking lesion talk you out of noticing what's actually changed.
See you next week, Derm community!
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DERM Community | Derm for Primary Care Team
