Figure 1.

Histological grade of breast cancer as assessed by the Nottingham Grading System. (a) A well-differentiated tumor (grade 1) that demonstrates high homology to the normal breast terminal duct lobular unit, tubule formation (>75%), a mild degree of nuclear pleomorphism, and low mitotic count. (b) A moderately differentiated tumor (grade 2). (c) A poorly differentiated (grade 3) tumor with a marked degree of cellular pleomorphism and frequent mitoses and no tubule formation (<10%).