Fine-tuned 2015 CNN beats GPT-6 and Claude on skin lesion diagnosis, 62% vs 42%

lmoroney · x · 2026-10-26

Dermatologist Magnus Lynch fine-tuned a 2015 Inception v3 CNN for 20 minutes and tested it against GPT-6 Astra and Claude Fable 5.1 on 200 biopsy-proven skin lesions from the public MILK10k dataset. The old CNN got the first-choice diagnosis right 125/200 times (62%), vs 84 (42%) for GPT-6 Astra and 85 (42%) for Claude Fable 5.1. Caveats: small sample, all hard biopsy-level cases, and the CNN isn't state of the art — yet the pattern holds: fine-tuned narrow specialists can beat prompted frontier giants on fixed labeling tasks. Laurence Moroney's writeup covers when to still build narrow models and a simple rule for choosing which to try first.

Related event: 20-Minute Fine-Tuned 2015 CNN Beats GPT-6 and Claude at Skin Lesion Diagnosis(3 posts)→

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