The St. Anne-Mayo grading system, also known as the Daumas-Duport grading system, introduced in 1988 was for a time a popular system for grading diffuse astrocytomas but has now been replaced by the WHO grading system which, however, was derived from the St Anne-Mayo system and thus shares many similarities 1-3.
Classification
The St. Anne-Mayo grading system is a 4 tiered system and uses the presence of 4 morphologic criteria to assign a grade:
nuclear atypia
mitosis
endothelial proliferation - 'piled-up' endothelial cells. NOT hypervascularity
necrosis
The grade then depends on the accumulation of these criteria as follows:
grade 1: 0 criteria
grade 2: 1 criterion (usually nuclear atypia)
grade 3: 2 criteria (usually nuclear atypia and mitosis)
grade 4: 3 or 4 criteria
Note that, unlike the WHO classifications up to and including the revised 4th edition (2016) that used Roman numerals, the St. Anne-Mayo system used Arabic numerals. This has been adopted by the 5th edition of the WHO classification (2021) 5.
History and etymology
Named after Catherine Daumas-Duport, a French pathologist 2 from Sainte Anne hospital who also worked together with the Mayo-Clinic in the United States 4.