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.



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.