Endocrine Abstracts

Introduction

Radioiodine whole-body scintigraphy plays an important role in the follow-up of patients with differentiated thyroid carcinoma (DTC), as it is highly accurate in detecting thyroid residues and recurrent disease. Unusual 131-iodine uptake outside the thyroid bed and areas of physiological uptake is strongly suggestive of distant metastasis. However, uncommon uptake may occur and lead to diagnostic errors.

Case report

A 45-year-old woman with a history of DTC underwent total thyroidectomy and dissection of the involved lateral neck compartment in 2005. The anatomopathological examination revealed papillary thyroid right lobe carcinoma with 25 mm - pT1b N1a Mx (8th Edition AJCC TNM Staging). She received two 131-iodine treatments in 2005 and 2006. The second post treatment whole-body scan showed a focal uptake in the left pelvic cavity. A CT scan and transvaginal ultrasound were performed, that showed a 5.6 cm cystic lesion in the left ovary. She underwent total hysterectomy and bilateral adnexectomy in 2007. The histological examination revealed an endometriosis cyst. A radioiodine whole-body scan was performed a year later and there were no areas of abnormal uptake. The patient is being kept under surveillance with no evidence of recurrent disease.

Discussion

We present a case of unusual 131-iodine uptake in the pelvic region, originated by an endometriosis cyst in the left ovary. This entity is a rare cause of incidental uptake of iodine-131, whose mechanism is not yet completely understood. Anomalous uptake in the pelvic region requires a gynaecological evaluation and complementary tests.