Does pelvic magnetic resonance imaging differentiate among the histologic subtypes of uterine leiomyomata?

OBJECTIVE

To evaluate if pelvic magnetic resonance imaging (MRI) is reliable for differentiating leiomyoma subtypes.

DESIGN

Prospective study.

SETTING

Academic center.

PATIENT(S): Forty-five patients underwent MRI before surgery for leiomyomata.

INTERVENTION(S): One radiologist blinded to patient history and histologic diagnosis recorded the MRI characteristics and classification of the largest leiomyoma.

MAIN OUTCOME MEASURE(S): Comparison of MRI and histologic diagnoses.

RESULT(S): Leiomyoma subtypes were diagnosed accurately by MRI in 69% of cases. Magnetic resonance imaging had a 95% sensitivity and 72% specificity for diagnosing an uncomplicated leiomyoma and a 10% sensitivity and 100% specificity for a cellular leiomyoma. For cystic leiomyomata, the sensitivity was 80% and specificity was 98%, and for hemorrhagic leiomyomata, 100% and 86%, respectively. Magnetic resonance imaging correctly diagnosed all malignant tumors and did not incorrectly diagnose a leiomyoma as a leiomyosarcoma in any case. Ill-defined MRI margins were significantly more likely to be leiomyosarcoma, whereas well-defined margins were characteristic of benign lesions. Hemorrhagic leiomyomata were significantly more likely to be hyperintense on T1-weighted images than other subtypes.

CONCLUSION(S): Although MRI is only fairly accurate in differentiating the subtypes of benign uterine smooth muscle tumors, signal intensities and margin characteristics are useful to distinguish accurately benign from malignant tumors.