Peritoneal strumosis: Presentation and management with multiple radioactive iodine treatments

Background: Struma ovarii is a rare benign ovarian teratoma comprising of thyroid tissue. Infrequently, benign struma ovari can present with extra ovarian dissemination, thus posing a treatment challenge. Here we describe a case of peritoneal strumosis treated with thyroidectomy and two courses of radioiodine ablation. Case presentation: 70 year old female with history of bilateral salphingo-oophorectomy 30 years prior presented with elevated thyroglobulin levels. Computed Tomography of the chest, abdomen and pelvis showed multiple peritoneal lesions. Subsequent biopsy revealed benign thyroid tissue. Thyroidectomy revealed papillary thyroid carcinoma; however, it did not match the peritoneal lesions. She was subsequently treated with radioiodine in two doses, each 30 mCi, 20 months apart. Follow up imaging and thyroglobulin levels showed a significant response to radioactive iodine treatment. Conclusion: Peritoneal Strumosis is a rare presentation of extra ovarian struma ovarii with benign thyroid histology. We propose a treatment paradigm similar to a thyroid malignancy, including total thyroidectomy and radioactive ablation with I-131. Moreover, radioactive ablation can be performed in stages with smaller doses to avoid radiation-induced side effects with an excellent response.