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

Abstract

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.

False-positive radioiodine uptake after radioiodine treatment in differentiated thyroid cancer

“…Overall, the literature showed 145 case reports and two series regarding false-positive 131 uptake after RIT For the reasons stated above, we excluded 129 papers, considering only those in which SPECT/CT was performed. A total of 18 papers were thus included: 1 series [17] and 17 case reports [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34]. The series reported 23 cases of falsepositive results: 15 in the chest, six in the pelvis, one in the cranium, and one in the abdomen.…”

“…Overall, 20 cases regarded radioiodine uptake in the chest: 11 in the lung (mainly inflammatory), four on the chest bones or on soft tissue due to inflammation/trauma, one in the thymus, one mesenchymal tumor and the rest in not well-characterized sites [17][18][19][20][21]34]. A total of 15 cases regarded uptake in the abdomen/pelvis: six in the kidney (cysts), five in the ovary (teratoma, benign cysts and malignant disease), two in the uterus and the others in not well-characterized sites [22][23][24][25][26][27][28][29]. Three cases reported uptake in the head: two surgical clips, and one on one eye [30,31,33].…”

“…The unusual site of the imaging, as reported above, and/or the inappropriate correlation between the burden of the metastasis and the serum Tg values as an inadequate response to RIT, could be a reason for suspecting a false-positive. In one case, Tg levels were high, which then decreased after surgical asportation of an ovarian cyst [22], and surprisingly, the same authors raised concerns regarding the true nature of the ovarian cyst.…”

“…However in all cases, diagnosis was possible by SPECT/CT and other imaging techniques. In four cases [17,[22][23][24], all were in the pelvis, diagnosis was virtually impossible, and surgery had to be performed to clarify the histology. Table 1 reports the possible causes of false-positive imaging, possible sites in SPECT/CT, and possible actions for reaching a diagnosis.…”