Prediction of Histopathologic Features and Proliferative Activity of Uterine Leiomyoma by Magnetic Resonance Imaging Prior to GnRH Analogue Therapy: Correlation between T2‐Weighted Images and Effect of GnRH Analogue

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Abstract
To predict the histological features and proliferative activity of leiomyomas and to evaluate the effect of GnRH analogues (GnRHa) by MR images, the correlation between MR images and histopathologic findings was studied on 137 leiomyomatous nodules from 79 patients. The correlation among cellularity, proliferative activity and MR images was studied on sections of 42 leiomyomatous, nodules stained with hematoxylin-eosin and immunohistochemistry for proliferating cell nuclear antigen. The utility of MR imaging in assessing response to therapy with a GnRHa (buserelin 900 μg/day, intranasal for 16 weeks) was studied on 62 leiomyomatous nodules from 29 patients. On T2-weighted MR images, we encountered five major images. According to the increase of signal intensity relative to that of the myometrium and/or the endometrium, the images were classified as Type 1, Type 2, Type 3, Type 4, and Type 5. Histopathologically, the majority of Type 1, Type 2 and Type 3 images had features of typical leiomyoma. Almost all cellular leiomyomas and bizarre leiomyomas had Type 4 images. Variable degenerative features were observed in the nodules with Type 5 images. According to the increase of signal intensity, leiomyomas had a tendency to show a high degree of both cellularity and proliferative activity. Moreover, the reduction rate of leiomyomatous nodules after GnRHa therapy correlated with the tumor signal intensity on T2-weighted images before therapy. The reduction rate was the lowest in Type 1 images (20.9%) and the highest in Type 4 images (50.7%). These results suggest that increased the signal intensity on T2-weighted MR images correlates with the cellularity and proliferative activity of leiomyomas, and with tumor response to GnRHa treatment. MR imaging enables quantitative monitoring of GnRHa therapy in patients with leiomyomatous nodules, and allows us to predict the histopathology, cellularity, proliferative activity, and shrinkage rate of nodules before GnRHa treatment.