Errors in the interpretation of Mohs histopathology sections over a 1-year fellowship

Errors can occur in the interpretation of Mohs histopathology sections. Errors in histology interpretation can lead to incomplete removal of cancer and cancer persistence or the unnecessary removal of uninvolved tissue. Extensive proctored training is necessary to reduce these errors to an absolute minimum level.

To analyze and quantify the number of cases and the amount of time required to reach a satisfactory level of expertise in the reading and interpretation of Mohs histopathology.

A single-institution pilot study was designed to track errors in the interpretation and mapping of Mohs histopathology sections. A Mohs surgery fellow independently preread Mohs cases and rendered his interpretation on the Mohs map. One of the Mohs program directors subsequently reviewed and corrected all cases. Errors were scored on a graded scale and tracked over the 1-year fellowship to determine the number of cases and amount of time necessary to reduce errors to a baseline minimal level.

One thousand four hundred ninety-one Mohs surgery cases were required to generate 1,347 pathology specimens for review and grading over 6 months of Mohs surgery fellowship before reducing errors to a minimum acceptable level of less than 1 critical error per 100 cases read.

The number of cases and time required to reduce errors in the interpretation of Mohs histology is substantial. Direct and immediate mentored correction of errors is essential for improvement. These results can act as a guide for Mohs surgery training programs to help determine the minimum number of directly proctored cases required to obtain expertise in this crucial component of Mohs surgery.