Application of the Kaiser score by MRI in patients with breast lesions by ultrasound and mammography

Abstract

PURPOSE This study aimed to verify whether the use of the Kaiser score can improve the diagnostic performance in breast magnetic resonance imaging (MRI) for suspicious lesions and avoid further invasive diagnostic approaches. METHODS This retrospective study enrolled 97 patients who underwent breast MRI before undergoing breast biopsy or surgery. Evaluations were conducted on all MRI images individually by 2 radiologists using the Kaiser score. Neither radiologist had the knowledge of the final histopathological diagnosis. The ability of the Kaiser score in diagnosis was established via a receiver performing characteristic (ROC) analysis, which was measured by the area under the ROC curve (AUC). Youden index was used to define the optimal cutoff value. Kaiser score categories were dichotomized into positive (cutoff score > 4) and negative scores (cutoff score ≤ 4). Cohen's kappa coefficient was used to analyze the inter-rater agreement. RESULTS Histopathology revealed 56 malignant and 41 benign lesions. The AUC for all lesions evaluated by the Kaiser score was 0.992 (95% CI: 0.981-1.0) and 0.958 (95% CI: 0.920-0.996) for 2 radiologists, respectively. Inter-rater agreement of the dichotomized Kaiser score was excellent (κ=0.894, P < .001). A total of 20 lesions (33.8%) previously categorized as BI-RADS 4 were reduced to BI-RADS 2/3 (19 benign lesions and 1 malignant lesion). CONCLUSION The Kaiser score is a valuable auxiliary diagnostic tool for improving the diagnostic ability of radiologists, whose experiences in breast MRI are diverse. In some cases, the application of the Kaiser score could possibly avoid unnecessary breast biopsies.

Figure 1.

Kaiser score flowchart: The Kaiser score is assigned by following a simple flowchart from the top to the bottom, which lets the reader assign the presence or absence of 4 diagnostic criteria.

Figure 2. a-f.

Representative axial slices of T2-TIRM sequence (a), apparent diffusion coefficient (ADC) image (b), early (c) and (b), delayed (d) post-contrast T1-weighted sequences, and signal-intensity time curve (e) and flowchart (f) are shown. A mass lesion presented with absent root sign, persistent enhancement, circumscribed margin, and high ADC (2.5 × 10⁻³ mm/s), classified as Kaiser score 1. Pathological diagnosis revealed a fibroadenoma.

Figure 3. a-f.

T2 TIRM sequence (a), ADC image (b), early (c) and delayed (d) post-contrast T1-weighted sequences and signal-intensity time curve (e) and flowchart (f) are shown. A mass lesion in the left breast of a 52-year-old female shows no root sign, a washout enhancement curve type, and homogeneous internal enhancement that corresponds to a Kaiser score of 4. The patient requested surgery that revealed an intraductal papilloma.

Figure 4. a-f.

Representative axial slices of T2 TIRM sequence (a), ADC image (b), early (c) and delayed (d) post-contrast T1-weighted sequences, and signal-intensity time curve (e) and flowchart (f) are shown. A mass lesion presented with root sign, plateau enhancement, diffuse ipsilateral edema and was classified as Kaiser score 10. Pathological diagnosis revealed an invasive ductal carcinoma.

Figure 5.

Receiver-operating characteristic (ROC) curves of all lesions the Kaiser score.

Figure 6. a-f.

Representative axial slices of T2 TIRM sequence (a), ADC image (b), early (c) and delayed (d) post-contrast T1-weighted sequences, signal-intensity time curve (e) and flowchart (f) are shown. The false-negative lesion (with a diameter of 0.5 cm) was formerly classified as Kaiser score 4 because its tiny root sign had been ignored. Pathological diagnosis revealed an invasive ductal carcinoma.