For many years it was noted that tumor differentiation corresponded to prognosis.  Bloom and Richardson in 1957 published the first widely known study, which showed that taking into account nuclear atypia, tubule formation, and mitotic activity of the tumor could result in a numeric grading system.

Each of the following was scored on a scale of 1–3.  Then, the 3 separate criteria or added together for a single score, which ranged from 3-9.  The 3 histologic factors were evaluated for presence in slight, moderate, or marked degree.

Total points of 3–5 was considered low grade (I), 6–7 was considered intermediate grade (II), and 8–9 was considered high grade (III).  The system of grading showed prognostic significance, but was significantly limited by inter-observer variability and reproducibility issues.  Subsequently, the Bloom-Richardson grading system was further refined in the Nottingham/Tenovus Primary Breast Cancer Study (1974) into what is now referred to as the Nottingham grading system.  The Nottingham grading system (revised Bloom-Richardson grading) is a semi-quantitative evaluation with better inter-observer reproducibility and evaluation criteria.