Quality Control of Patho-Anatomical Diagnosis of Carcinoma of the Breast

Abstract

Three pathologists, especially interested in breast cancer, reexamined 379 random specimens of invasive breast cancer initially diagnosed at 27 pathological institutes; these were obtained from the computer register of the Danish Breast Cancer Cooperative Group (DBCG). The degree of variation between a) the primary diagnosis (the country as a whole) and each of the 3 pathologists and b) between the 3 pathologists mutually, has been studied with regard to the 2 main groups of carcinoma—infiltrating duct carcinoma (IDC) and infiltrating lobular carcinoma (ILC). The degree of variation was found to be similar between each of the 3 pathologists and the country as a whole, with a kappa value of approx. 0.3 for both types of carcinoma, and a considerably better interobserver variation between the 3 pathologists with a kappa value of approx. 0.7. The most important reason was that the 3 pathologists agreed on the occurrence of more than twice as many cases primarily diagnosed as ILC. A partial explanation is in fact that since the start of DBCG, reports have appeared of variants of ILC not previously known. The diagnosis of malignancy (carcinoma) was almost completely unambiguous.

Key Words:

• Breast cancer
• histopathology
• quality control