In this episode, Dr. Ian Cree, Head of The WHO Tumour Classification discusses his team's recent open access publication in Modern Pathology. Historically, mitotic figures counting has been done by expressing the number of mitoses per n high power fields (HPFs), ignoring the fact that microscope fields may differ substantially, even at the same high power (×400) magnification. Dr. Cree and coauthors remind all of this variation and its implication on the accuracy of our diagnostic and tumor grading practices. While the expanding adoption of computational digital pathology algorithm will help bring consistency to assessing proliferation activity, our MODPATH Chat guest recommends that counting should be performed per standard international unit of (mm2); with an indication of the area to be counted and the method used (“hotspot” vs “average”). Study by Cree et al, Counting mitoses: SI(ze) matters! Modern Pathology, 34, 1651–1657 (2021). https://www.nature.com/articles/s41379-021-00825-7. Our GDPR privacy policy was updated on August 8, 2022. Visit acast.com/privacy for more information.