Abnormal radioiodine uptake on post-therapy whole body scan and sodium/iodine symporter expression in a dermoid cyst of the ovary: report of a case and review of the literature

Radioiodine whole body scan pitfalls in differentiated thyroid cancer

PURPOSE

whole body scan (WBS) performed following diagnostic or therapeutic administration of I-131 is useful in patients with differentiated thyroid carcinoma. However, it can be falsely positive in various circumstances. We aimed to report a series of pitfalls in a clinical perspective.

METHODS

A search in the database PubMed utilizing the following terms: "false radioiodine uptake" and "false positive iodine 131 scan" has been made in January 2023. Among the 346 studies screened, 230 were included in this review, with a total of 370 cases collected. Physiological uptakes were excluded. For each patient, sex, age, dose of I-131 administered, region and specific organ of uptake and cause of false uptake were evaluated.

RESULTS

370 cases of false radioiodine uptake were reported, 19.1% in the head-neck region, 34.2% in the chest, 14.8% in the abdomen, 20.8% in the pelvis, and 11.1% in the soft tissues and skeletal system. The origin of false radioiodine uptake was referred to non-tumoral diseases in 205/370 cases (55.1%), benign tumors in 108/370 cases (29.5%), malignant tumors in 25/370 cases (6.7%), and other causes in 32/370 cases (8.7%).

CONCLUSIONS

WBS is useful in the follow-up of patients with differentiated thyroid carcinoma, however it can be falsely positive in various circumstances. For this reason, it is critically important to correlate the scintigraphic result with patient's medical history, serum thyroglobulin levels, additional imaging studies and cytologic and/or histologic result.

Concurrent Benign Iodine-Avid Thymic and Liver Cysts Mimicking Metastatic Disease on 131I Whole-Body Scintigraphy

ABSTRACT

A 57-year-old woman received radioiodine therapy post total thyroidectomy for pT3aNxMx follicular thyroid carcinoma. Posttherapy 131I whole-body scan showed 131I concentration in the chest, mediastinum, and left upper thigh with stimulated thyroglobulin (Tg) of 89 μg/L. Subsequent radioiodine therapies showed persistent 131I accumulation in the anterior mediastinal soft tissue lesions and a hypodense segment VII liver lesion visualized on SPECT/CT, suggestive of iodine-avid metastatic disease despite the undetectable serum Tg (<1.0 μg/L) with no Tg antibody interference. Biopsy of the liver lesion revealed liver cyst, and consequent removal of the mediastinal lesions showed benign thymic cysts.

Aberrant Radioactive Iodine Uptake in Simple Ovarian Cyst: A Rare Finding

I-131 whole body scan and therapy play an important role in the follow-up of differentiated thyroid carcinoma patients for the detection of residual thyroid tissue and metastatic disease. However, various false-positive findings have been reported in the literature which can appear as metastases. Here, we present one such case, in which an I-131 posttherapy scan revealed false-positive radioactive iodine uptake which localized to a simple ovarian cyst.

False-Positive Radioiodine Uptake in Simple Ovarian Cyst in a DTC Patient: A Case Report

Abnormal radioildine uptake can be caused by various pelvic lesions in differentiated thyroid cancer patient. Here we presented an abnormal uptake in the left side of the pelvic cavity on postablative I-131 scintigraphy in a 51-year-old woman with history of stage T1aN1M0 papillary thyroid cancer. The SPECT/CT fused imaging revealed the lesion in the left ovary. Laparoscopic bilateral adnexectomy showed a left ovarian mass (5 cm) and pathologic finding showed a simple ovarian cyst. The nonstimulated Tg immediately decreased to 143 ng/ml after bilateral adnexectomy 3 days later and to 0.109 ng/ml after 4-month follow-up. Timely intervention measures are very necessary for patients with ovarian cyst with abnormally elevated Tg level.

Surveillance for Differentiated Thyroid Cancer Recurrence

Serum thyroglobulin monitoring along with anatomic and functional imaging play key roles in the surveillance of patients with differentiated thyroid cancer after initial treatment. Among patients with a disease stage justifying thyroid remnant ablation or with suspected metastatic disease, radioiodine whole-body scans are essential in the months after surgery. For patients with low to moderate-risk cancers, ultrasonography of the neck (with measurement of serum thyroglobulin on thyroid hormone replacement) are the best initial diagnostic modalities, and are often the only tests required. In individuals suspected of having distant metastases, CT, MRI, and 18F-FDG PET can make important contributions in localizing residual disease and monitoring its progression and responses to therapy, provided they are used in the appropriate setting.