Confocal microscopy matched histology on Mohs margins

Design

Prospective interventional diagnostic study

Population

39 patients, 42 non-melanoma skin cancers, 261 Mohs margins

Primary outcome

Agreement with histopathology and between readers

Effect

Accuracy 96.4%; inter-reader kappa 0.86 for margins

A prospective Italian study examined 261 margins from 42 non-melanoma skin cancers in 39 patients having Mohs surgery, using ex vivo fluorescence confocal microscopy in a digital stain mode that produces haematoxylin-and-eosin-like images. A dermatologist and a pathologist read each margin independently and blind.

Agreement between the two readers was almost perfect for margins (kappa 0.86, 98.6% observed agreement) and tumour type (kappa 0.88). Against conventional histopathology, overall accuracy was 96.4%, with one false-negative margin and one discordance from sample processing.

Confocal imaging avoids frozen-section preparation and could shorten Mohs turnaround. The single false negative is a reminder that it is not yet a replacement for histology in every setting.

The study did not measure time savings, and the equipment is costly and not widely available in India.

• Confocal imaging produced images that trained readers interpreted reliably.
• Readers needed specific training; agreement relied on it.
• One margin was falsely called clear; keep histological confirmation where pathways require it.
• Workflow gains have not yet been measured.

Why it matters

It points to a margin check that skips the cryostat.

The statistics, in plain English

Kappa above 0.8 is conventionally called almost perfect agreement. An accuracy of 96.4% across 261 margins still left one positive margin missed.

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