Invasive Ductal CA : Tubule Formation
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. Tubule/duct formation is a surrogate marker of the degree of glandular differentiation in invasive ductal carcinoma. It is assessed for the entire tumor at low magnification. Only the structures with clear-cut central lumina are counted. Scoring is done as follows: glands and tubules in >75% of the tumor (score 1), 10%-75% of tumor (score 2), and <10% of the tumor (score 3). This case of invasive ductal carcinoma showed tubule formation in 30% to 40% of the tumor and was assigned a score of 2 for tubule formation.