The current grading system for cancerous tumors is credited to Dr. Albert Broders of Mayo's pathology staff. In 1920, Dr. Broders published the first of four papers describing a system of microscopically grading cancers based on a numerical system. Cancers of the least malignancy were designated as a grade 1; cancers of the highest malignancy were given a grade 4.

Dr. Broders' study of 537 cases was the beginning of an index of malignancy that hospitals worldwide have adopted. The index brought international recognition to its author and to Mayo. Dr. Broders joined the staff of Mayo Clinic in 1912 as an assistant in surgical pathology. He advanced to an associate in pathology and to head of Section in Surgical Pathology in 1922. He served as Director of Surgical Pathology at Mayo Clinic from 1945 until his retirement in 1950.

In addition to his development of the cancer grading index, he also modified in 1931 the fresh frozen tissue technique that was originally developed for surgical use at Mayo Clinic by Dr. Louis B. Wilson.