The diverse pathology and kinetics of mass, nonmass, and focus enhancement on MR imaging of the breast

Abstract

Purpose: To compare the pathology and kinetic characteristics of breast lesions with focus-, mass-, and nonmass-like enhancement.

Materials and methods: A total of 852 MRI detected breast lesions in 697 patients were selected for an IRB approved review. Patients underwent dynamic contrast enhanced MRI using one pre- and three to six postcontrast T(1)-weighted images. The "type" of enhancement was classified as mass, nonmass, or focus, and kinetic curves quantified by the initial enhancement percentage (E(1)), time to peak enhancement (T(peak)), and signal enhancement ratio (SER). These kinetic parameters were compared between malignant and benign lesions within each morphologic type.

Results: A total of 552 lesions were classified as mass (396 malignant, 156 benign), 261 as nonmass (212 malignant, 49 benign), and 39 as focus (9 malignant, 30 benign). The most common pathology of malignant/benign lesions by morphology: for mass, invasive ductal carcinoma/fibroadenoma; for nonmass, ductal carcinoma in situ (DCIS)/fibrocystic change(FCC); for focus, DCIS/FCC. Benign mass lesions exhibited significantly lower E(1), longer T(peak), and lower SER compared with malignant mass lesions (P < 0.0001). Benign nonmass lesions exhibited only a lower SER compared with malignant nonmass lesions (P < 0.01).

Conclusion: By considering the diverse pathology and kinetic characteristics of different lesion morphologies, diagnostic accuracy may be improved.

Fig. 1

T₁ weighted axial post-contrast subtraction images demonstrating: a) mass-like enhancement in a 47 year old woman representing IDC, b) nonmass-like enhancement in a 54 year old woman representing DCIS, and c) focus enhancement in a 61 year old woman representing DCIS.

Fig. 2

Representative kinetic curves of malignant and benign lesions of each enhancement type: a) mass-like enhancement: malignant IDC and benign fibrocystic change (FCC), b) nonmass-like enhancement: malignant DCIS and benign FCC, and c) focus enhancement: malignant DCIS and benign FCC.

Fig. 3

BIRADS qualitative descriptors of a) initial rise and b) delayed phase, in mass, nonmass and focus lesions overall, as well as benign and malignant subtypes.

Fig. 4

ROC curves of the parameter SER in focus lesions (dashed line), mass lesions (dark grey line), and nonmass lesions (light grey line). This plot demonstrates improved diagnostic performance of SER in mass compared with nonmass and focus lesions.