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- Presentation
Rethinking Melanoma In Situ: Diagnosis, Classification, and Patient Impact
Description
The speaker argues that it may be time to rethink the diagnosis and terminology of melanoma in situ (MIS), drawing on a memorable patient with extensive skin cancer history whose forehead lesion turned out to be MIS alongside multiple invasive melanomas. He reviews the historical evolution of MIS, noting that early expert work helped define it, but later molecular studies showed MIS shares genetic features more closely with severely atypical nevi than with invasive melanoma. He explains how modern WHO classification and the MPATH-Dx system have shifted melanocytic lesions into pathway-based, risk-stratified categories, with MIS increasingly grouped as a high-grade but noninvasive lesion rather than true melanoma. The talk also highlights problems with diagnostic reproducibility, especially for intermediate categories, and the 2023 MPATH-Dx revision that simplified reporting and separated low-grade from high-grade lesions. Finally, he discusses why naming matters: MIS and thin melanomas can drive substantial healthcare costs, overdiagnosis concerns, and significant patient anxiety, with psychosocial distress similar across MIS and invasive melanoma diagnoses. He concludes that a less alarming, more precise terminology may better reflect biology and reduce harm to patients.
View moreConclusions
- Melanoma in situ is best understood as a borderline, biologically intermediate melanocytic lesion that is closer to severely atypical nevi than to invasive melanoma.
- Genetic and histologic evidence supports a stepwise progression model in melanoma, with accumulating driver mutations and later loss of tumor suppressors accompanying invasion.
- Modern classification systems such as WHO pathways and MPATH-Dx increasingly place melanoma in situ within a high-grade dysplastic or atypical category rather than treating it as straightforward invasive cancer.
- The original MPATH-Dx five-class scheme had poor reproducibility, especially for the moderate-atypia category, leading to a simplified revised system.
- A growing body of expert opinion argues that some MIS and very-low-risk pT1a melanomas should be renamed to reduce overtreatment and better reflect their low malignant potential.
- Overdiagnosis of melanoma in situ is common and creates substantial unnecessary healthcare costs.
- Receiving a diagnosis of melanoma in situ causes meaningful psychosocial distress that is often similar to the distress caused by more advanced melanoma diagnoses.
- Using more precise, less alarming terminology may reduce patient anxiety and improve communication without compromising care.
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