Native T1 mapping of the breast in MRI to differentiate fibroadenomas from benign phyllodes tumors: a preliminary study

Objective: Both fibroadenomas (FAs) and phyllodes tumors (PTs) are classified as fibroepithelial lesions. PTs are rare fibroepithelial neoplasms that have a morphologic spectrum ranging from benign to malignant. The differentiation of these entities is important as PTs are to be enucleated surgically. The purpose of this study was to calculate the T1 relaxation times of fibroadenomas and phyllodes tumors and assess the potency of native T1 mapping for the differentiation of these tumors. Materials and methods: This prospective study included 11 patients with a proven diagnosis of benign PT and 14 patients with a proven diagnosis of FA. All the patients underwent T1 mapping prior to conventional dynamic contrast-enhanced MRI (DCE-MRI). Two radiologists, in consensus, selected lesion locations using freehand regions of interest from the DCE images and copied them onto T1 maps to acquire T1 relaxation times. The T1 relaxation times of the FA and PT groups were compared statistically. Results: The mean T1 relaxation times were higher in the PT group compared to the FA group (p ≤ 0.001). The receiver operating characteristic analysis showed that the T1 relaxation time being longer than 1,478 ms differentiated PTs from FAs with a sensitivity of 0.89, specificity of 1, and area under the curve value of 0.93. Conclusion: We found that benign PTs had longer relaxation times in T1 mapping compared to FAs. Native T1 mapping can be used to differentiate PTs from FAs and adding T1 mapping in breast MRI in cases with fast-growing fibroepithelial lesions or multiple fibroepithelial lesions can facilitate the decision-making process. © 2021, European Society for Magnetic Resonance in Medicine and Biology (ESMRMB).