Malignancy rates of B3-lesions in breast magnetic resonance imaging - do all lesions have to be excised?

Abstract

Background: Approximately 10% of all MRI-guided vacuum-assisted breast biopsies (MR-VAB) are histologically classified as B3 lesions. In most of these cases surgical excision is recommended. The aim of our study was to evaluate the malignancy rates of different B3 lesions which are visible on MRI to allow a lesion-adapted recommendation of further procedure.

Methods: Retrospective analysis of 572 consecutive MR-VAB was performed. Inclusion criteria were a representative (=successful) MR-VAB, histologic diagnosis of a B3 lesion and either the existence of a definite histology after surgical excision or proof of stability or regression of the lesion on follow-up MRI. Malignancy rates were evaluated for different histologies of B3 lesions. Lesion size and lesion morphology (mass/non-mass enhancement) on MRI were correlated with malignancy.

Results: Of all MR-VAB 43 lesions fulfilled the inclusion criteria. The malignancy rate of those B3 lesions was 23.3% (10/43). The highest malignancy rate was found in atypical ductal hyperplasia (ADH) lesions (50.0%; 4/8), 33.3% (2/6) in flat epithelial atypia (FEA), 28.6% (2/7) in lobular intraepithelial neoplasia (LIN) and 12.5% (2/16) in papillary lesions (PL). All 6 complex sclerosing lesions were benign. Mass findings were significantly more frequently malignant (31.3%, 10/32; p < 0.05) than non-mass findings (0/11). Small lesions measuring 5-10 mm were most often malignant (35.0%; 7/20). All large lesions (> 20 mm) were not malignant (0/10). Intermediate sized lesions (11-20 mm) turned out to be malignant in 23.1% (3/13).

Conclusions: The malignancy rate of B3 lesions which were diagnosed after MR-VAB was 23.3%. ADH, FEA and LIN showed considerable malignancy rates (50%, 33% and 29%) and should therefore undergo surgical excision. None of the cases, which were diagnosed as radial scars, non-mass enhancement or larger lesions (> 20 mm) were malignant. Here, a follow-up MRI seems to be advisable to avoid unnecessary operations.

Trial registration: Retrospective study design, waived by the IRB.

Keywords: B3 lesions; Breast MRI; MRI-guided breast biopsy; Vacuum-assisted biopsy.

Fig. 1

Non-mass enhancement of 90 mm (subtraction images) in the upper outer quadrant of the left breast. MR-guided VAB (in 40 mm nipple distance, arrow) revealed benign histology (radial scar)

Fig. 2

Non-mass enhencement measuring 60 mm (subtraction images) in the lower outer quadrant of the left breast. MR-VAB had benign histology (papillary lesions and FEA) as a result

Fig. 3

Subtraction images with contrast-enhancing mass lesion of 7 mm (arrow) in the upper outer quadrant of the right breast, which showed atypical epithelial proliferation of ductal type (B3) on MR-guided biopsy, but proved to be invasive ductal carcinoma (grade 2) on final histology

Fig. 4

Irregular shaped mass lesion (subtraction images) in the upper outer quadrant of the right breast with a size of 13 mm. MR-guided VAB showed papillary lesion and ADH on histopathology, but final histology confirmed low grade DCIS

Fig. 5

MR-guided VAB of this 15 mm measuring mass lesion (subtraction images) in the lower inner quadrant of the right breast showed benign histology (radial scar in association with lobular intraepithelial neoplasia)

Fig. 6

This 8 mm measuring mass lesion (subtraction images) in the center of the left breast had benign histology (radial scar)