Invasive Ductal CA : Nuclear Grade
The modified Scarff-Bloom Richardson grading system (Nottingham Combined Histologic Grade) is based on the degree of tubule/duct formation, nuclear grade, and mitotic rate.
Nuclear features are assessed in the area with greatest pleomorphism. The tumor nuclei are compared to the nuclei of normal ductal epithelial cells in the adjacent breast tissue. The nuclei are subdivided into three categories: 1) low-grade nuclei (score 1) are small, uniform and comparable in size to those of normal ductal epithelial cells. The chromatin is evenly dispersed and nucleoli are inconspicuous. 2) intermediate grade nuclei (score 2) are 1.5-2x the size of benign ductal epithelial nuclei. They show mild to moderate pleomorphism and small punctate nucleoli. 3) high-grade nuclei (score 3) are more than twice the size of benign ductal epithelial cells. There is marked pleomorphism, vesicular chromatin, and prominent nucleoli.
The tumor shown here has low-grade nuclei (score 1). Incidentally, it also showed tubule formation throughout its extent (score 1) and low mitotic activity (score 1) giving a combined score of 3 (well-differentiated; Grade I by Nottingham combined histologic grade).