Accuracy of typing and grading invasive mammary carcinomas on core needle biopsy compared with the excisional specimen.

INTRODUCTION: Breast core needle biopsy (CNB) allows evaluation of histological, prognostic, and predictive factors in invasive mammary carcinomas (IMC). We tested the CNB accuracy on typing and grading of invasive breast carcinomas.
MATERIALS AND METHODS: A histological review of 120 CNBs and their related surgical specimens was carried out in a double-blind fashion. Tumor type and grade were assigned according to the World Health Organization classification and the Nottingham grading system.
RESULTS: The sum of CNB fragment lengths varied from 4 mm to 38 mm (mean 16.7 mm), and tumor sample size varied from 1 mm to 26 mm (mean 11.1 mm). Histological type matched surgical specimen evaluation in 80 of 120 cases (66.6%). Of the cases, 17 (14.2%) were changed to a different prognostic category. Histological grade comparison was accurate in 56 of 95 cases (59.0%, kappa=0.35). Histological grade components (tubule formation, nuclear grade, and mitotic index) agreed, respectively, in 54.7%, 58.9%, and 62.1% (kappa index 0.30, 0.36, and 0.28). DISCUSSION: Typing IMC on CNB can be routinely assessed based on good correlation with surgical specimens, especially considering prognostic categories for IMC. Grading IMC based on CNB is not as accurate, and its evaluation should be delayed until the surgical specimen examination. Tumor heterogeneity seems to be the most important factor for disagreement.