A Case of Struma Uteri

Case Report A 35-year-old woman was admitted to Kansai Medical University Hospital because of a uterine mass with pelvic pain. She had had five pregnancies and three full-term deliveries (one normal and two cesarean deliveries). At the first cesarean delivery 8 years previously, a mass was found attached to the uterus. On gynecologic examination, a large pelvic mass was found. A sonogram showed a complex mass in the postuterine region. CA125, CA130, SLX (Sialyl Lex-i antigen), and SCC (squamous cell carcinoma-related antigen) were within normal ranges. A thyroid function test was not performed before the procedure. After the procedure, the stock serum obtained preoperatively was measured, and the result of thyroid function was normal. MRI revealed a complex mass with small areas of T1 and T2 shortening and central areas of T1 and T2 prolongation in the postuterine region (Figs. 1A–1C). The ovaries were separate from the mass. We thought the lesion was a mass with hemorrhagic necrosis because of small areas of T1 and T2 shortening. Although the origin of the mass was not certain based on the images, we considered it to be a leiomyoma because a nondegenerated area within the lesion was hypointense, similar to the pelvic muscles on T2-weighted images. Also, hemorrhagic necrotic areas were occasionally seen in the leiomyoma, and subserosal leiomyoma often involved the parauterine region. Various sarcomas, including leiomyosarcoma, are also often seen as a mass with hemorrhagic necrosis in the postuterine region. In the current case, we thought they were inconsistent with the slow growth of the mass. During surgery, an 11-cm mass attached to the uterine cervix and vaginal wall was completely removed. The adnexa were normal. On section, the tumor consisted of a large central cystic part and a solid part with peripheral cystic hemorrhagic necrotic areas. No fat tissue was in the lesion. Microscopically, the mass consisted of a thyroid tissue composed of multiple follicles and stroma (Fig. 1D). The final histologic diagnosis was pure struma of the uterus. No evidence of malignant change was present in the struma uteri.