Uterine Inflammatory Myofibroblastic Tumor Mimicking Myoma Treated With Gonadotropin-Releasing Hormone Therapy: A Case Report

Inflammatory myofibroblastic tumors (IMTs) of the uterus are a rare entity that can be challenging to distinguish from leiomyomas, both radiologically and pathologically. No previous reports have documented the response of uterine IMT to gonadotropin-releasing hormone (GnRH) therapy. A 47-year-old Japanese woman presented to our hospital with excessive menstruation and uterine prolapse. Magnetic resonance imaging (MRI) revealed four well-demarcated uterine masses, with the largest measuring 81 mm. Myomas were suspected. Oral GnRH therapy was initiated to relieve the symptoms and reduce the preoperative volume. After four months, follow-up MRI showed a reduction in the largest mass to 62 mm and increased hyperintense areas on T2-weighted images. At six months, the patient underwent laparoscopic hysterectomy and colporrhaphy. Histopathological examination revealed that the largest tumor was an IMT with abundant myxoid matrix, positive for anaplastic lymphoma kinase (ALK), and ALK gene rearrangement. The remaining three masses were diagnosed as usual-type leiomyomas. This is the first reported case of uterine IMT treated with GnRH therapy, which resulted in notable tumor shrinkage. This case highlights both the potential therapeutic approach for uterine IMT and the diagnostic difficulty in distinguishing it from leiomyomas preoperatively.