[Phyllodes tumor of the breast with cystic portion: MR imaging with histopathological correlation]

The purpose of this study was to reassess the MR imaging appearance and significance of dynamic MR imaging in phyllodes tumor with cystic portion. MR imaging in four patients with surgically proven phyllodes tumor was reviewed both radiologically and histopathologically. In all cases, T2WI showed inhomogeneous signal intensity with a hypointense area and internal septation in the solid portion. At histopathological examination, collagenous fibers and hemorrhage were seen in the area corresponding to hypointensity in the solid portion on T2WI. In the dynamic study, three cases showed the gradual type and one the rapid type. The percentage of cystic portion in the gradual type was over 30%, and in the rapid type, 6%. Cases of the gradual type, histopathologically, showed apparent hemorrhage, necrosis, cystic dilatation of the duct, sclerotic change, and a less densely stromal component than the rapid type. In conclusion, we speculate that the dynamic pattern may reflect changes in tumor angiogenesis that do not correlate with either malignancy or benignancy. On T2WI, internal septation and a hypointense area are considered useful for diagnosis.