Can Breast MRI Differentiate Phyllodes Breast Tumors from Fibroadenomas?

Objective: The purpose of this study was to evaluate if MR imaging could differentiate phyllodes breast tumors and fibroadenomas. Materials and Methods: Dynamic contrast enhanced MR imaging was performed for six patients with six phyllodes breast tumors and results were compared with respect to morphology and contrast enhancement with those of 69 fibroadenomas of 50 patients. Results: Smooth margins were seen in 83.3% of the phyllodes tumors and 93% of the fibroadenomas and a round, oval or lobulated shape in 100% and 98.6%, respectively. A heterogeneous internal structure was observed in 50% of phyllodes tumors and in 33.3% of fibroadenomas. Cystic changes were found in 50% of phyllodes tumors and 3% of fibroadenomas. Most of both lesions appeared with high signal intensity on T2-weighted images. A significantly greater increase in signal was seen on T2-weighted images in the tissue surrounding one of the phyllodes tumors (16.7%). After the administration of contrast material, 33.4% of phyllodes tumors and 21.7% of fibroadenomas showed a suspicious signal intensity-time course. Conclusion: Phyllodes breast tumors and other fibroadenomas cannot be accurately differentiated on breast MR imaging.