MR imaging analysis of heterogeneous leiomyomas of the uterus.

Thirty-six leiomyomas from the same number of patients that were heterogeneous on MR imaging were evaluated for analyzing their MR patterns and for differentiating each type of secondary changes by means of MR imaging-pathologic correlation. The tumors with a mean diameter of 9 cm could be classified into 4 patterns depending on the morphological appearance of signal intensity: speckled (n = 14); nodular (n = 11); cystic (n = 9); or indeterminate (n = 2). Speckled pattern was associated with a mild degree of hyaline or myxoid degeneration or focal necrosis. Nodular pattern was caused by necrosis or cellular leiomyoma, and cystic pattern was related to severe hyaline or myxoid degeneration or necrosis. Each type of secondary changes within leiomyomas showed distinctive MR findings, if they were severely involved. However, use of an additional contrast-enhanced study was necessary in some instances for further clarification. MR imaging has a potential in distinguishing each type of secondary changes that occur in leiomyomas. Various degenerative changes occur in approximately 65% of uterine leiomyomas, and are caused mainly by alteration in the blood supply originating from rapid growth, pregnancy, mechanical accident, and postmenopausal atrophy. These changes include hyaline, mucoid, or myxoid degeneration, calcification, cystic changes, necrosis (red degeneration), and fatty metamorphosis. It is well known that the presence of degenerative changes within leiomyomas can be predicted on MR imaging by a heterogeneous signal intensity on T2-weighted images, although clear distinction of each type of degeneration can not be made by this modality. Recently, cellular leiomyoma, one of the variants of leiomyomas, was also reported to cause heterogeneous signal intensity. However, because various other uterine tumors can also have similar signal intensity on MR imaging, further evaluation for the heterogeneous leiomyomas appears to be necessary. The purpose of our study was to analyze the patterns of heterogeneous leiomyomas and to differentiate each type of secondary changes by means of MR imaging-pathologic correlation.