High-spatial-resolution MR imaging of focal breast masses: interpretation model based on kinetic and morphological parameters.

Objective: To assess a new interpretation model combining kinetic pattern and morphologic characteristics using high-spatial-resolution MR imaging.

Methods: Breast MR imaging was performed in 58 patients with 63 pathologically proved focal breast masses (49 malignant and 14 benign). MR imaging was performed on a 1.5-Tesla system using the volumetric interpolated breath-hold examination (VIBE) sequence. Morphological parameters were lesion shape, mass margin, rim enhancement (RE), enhancing internal septations, and internal signal on T2-weighted images. Lesion shape/margin was classified into four categories as follows: smooth (smooth/round or smooth/oval), lobulated (lobular shape), irregular (irregular margin or irregular shape), and spiculated (spiculated margin). RE was sub-classified as early RE at 60 sec and delayed RE at 4 min. Strongly high signal and the presence of internal black septations were evaluated over the entire lesion on T2-weighted images. The kinetic parameter was visually assessed as follows: washout, plateau, and progressive.

Results: The most frequent types of lesion shape/margin in the malignant lesions were irregular (47%) and spiculated (43%), whereas 13 of the benign lesions had smooth or lobular margins (93%). The most frequent characteristics in breast cancers with lobulated configuration were washout pattern (80%), whereas 78% of the lobulated benign lesions were negative for visual washout. The positive predictive value (PPV) was 98% (49/50).

Conclusions: "Washout with enhancing septations" is thought be specific for carcinoma with a lobulated configuration (80%). A combination of morphological criteria (including lesion shape/margins, strongly high signal on T2-weighted images) and visual washout is useful for differentiating between benign and malignant lesions.