Differentiation between benign phyllodes tumors and fibroadenomas of the breast on MR imaging

Purpose The purpose of this study was to determine the factors that contribute to the differentiation between phyllodes tumors (PTs) and fibroadenomas (FAs) on MR imaging. Materials and methods This retrospective study included 19 PTs and 18 FAs with ≥2 cm diameter. The presence or absence of a capsule and internal septum, the extent of lobulation, and the apparent diffusion coefficient (ADC) values were determined. The presence or absence of a cystic component, the time-intensity curve, and the signal intensity on delayed-phase contrast-enhanced T1WI were also evaluated in 31 patients (16 PTs and 17 FAs) who underwent a contrast-enhanced study. Results Cystic components were seen in 10 of the 16 PTs (63%) and in 4 of the 17 FAs (24%; P = 0.03). The PTs showed strong lobulation more frequently compared to the FAs (14/19 [74%] vs. 7/18 [39%], respectively; P = 0.04). Though there was no significant difference, PT tended to be heterogeneous more frequently on the delayed phase of the contrast-enhanced T1WI compared to the FA (11/16 [69%] vs. 7/17 [41%], respectively). No significant difference was found in the other findings. Conclusions Although PTs and FAs show similar MR findings, the presence of a cystic component, strong lobulation, and heterogeneity on delayed-phase contrast-enhanced T1WI suggests a PT.