MRI appearance of mesenchymal tumors of the uterus

Uterine leiomyomas are the most common uterine neoplasms. Statistically, a uterine mass with unusual imaging features is more likely to represent a leiomyoma than other uncommon uterine mesenchymal neoplasms such as leiomyosarcoma or endometrial stromal tumors. Several prior studies have attempted to identify objective imaging characteristics that differentiate these entities. The purpose of this study was to test these criteria on our patient population.

This retrospective study was approved by the institutional Human Investigations Committee and was performed in compliance with HIPAA regulations. Four patients with uterine leiomyosarcoma, two with stromal tumors of uncertain malignant potential (STUMP), one with endometrial stromal sarcoma, and two with mixed endometrial stromal and smooth muscle tumors were included in the study. Seventeen additional control cases of leiomyomas were selected as controls. Cases were blindly evaluated by two experienced readers. Objective criteria included T1 and T2 signal characteristics, enhancement pattern, the presence of cystic changes, and ill defined margins. Subjective criteria included individual reader gestalt. All cases had pathologic correlation.

None of the objective criteria were associated with the presence or absence of uterine mesenchymal neoplasm. Ill defined margins came closest to having statistical significance (p=0.06). Reader gestalt was statistically associated with the presence of mesenchymal neoplasm for one of our readers (p=0.02) but not for the other (p=0.07).

We found poor accuracy for objective imaging criteria in distinguishing leiomyomas with atypical imaging features from more clinically significant uterine mesenchymal neoplasms.