Histologic grade

The histological evaluation of the grade components (the mitotic count, nuclear pleomorphism, and tubule formation) was generally done according to the WHO classification (table 1; ref 1). The tumors were classified into the following three categories:

grade 1 = well diffentiated
grade 2 = moderately differentiated
grade 3 = poorly differentiated
grade 2-3 = moderately to poorly differentiated
not available = missing data or grade could not be assessed

Note 1: The histological parameters were determined by more than 50 pathologists at the respective pathology laboratories at the time of the diagnosis.

Feature	Score
Tubule formation
Majority of tumor (>75%)	1
Moderate degree (10-75%)	2
Little or none (<10%)	3
Nuclear pleomorphism
Small, regular uniform cells	1
Moderate increase in size and shape variability	2
Marked variation in shape	3
Mitotic counts
Rare	1
2-3	2
>3 per a high power field	3
3-5 points: Grade I - well differentiated
6-7 points: Grade II - moderately differentiated
8-9 points: Grade III - poor differentiated

Table 1. A summary of the semiquantitative method for assessing histological grade in breast cancer

1. World Health Organization. Histological typing of breast tumours. 2 ed. Geneva, Switzerland: World Health Organization; 1981.