Presentation
History of pT3b N1a M0, MACIS 6.79 papillary thyroid carcinoma received Thyrogen two days prior to receiving 150 mCi of I-131 s/p total thyroidectomy. Post ablative imaging was performed five days after the patient received I-131 therapy.
Patient Data
On follow up planar and SPECT/CT images a focus of increased uptake in the pelvis was seen. On SPECT/CT images this corresponded to the right uterine cervix.
Case Discussion
Iodine-131 post ablative imaging is the standard of care for visualisation of residual thyroid tissue or metastases. Normal uptake can be seen in the salivary glands, oropharynx, GI/GU tracts and breast tissue after surgical treatment for thyroid cancer.
Nabothian cysts are a very common benign, asymptomatic condition in women. The cause has been reported to be secondary to chronic inflammation and cellular metaplasia and subsequent cyst formation. Generally, they are found incidentally on pelvic ultrasound. Nabothian cysts have been reported to cause false positives in post Iodine ablation imaging as high as 25%.
False positives have also been reported in conditions such as hepatic and renal cysts, nasolacrimal cysts, thyroglossal duct cysts and epidermoid cysts.
Since distant metastases, especially in the pelvis, are rare in the setting of papillary thyroid cancer, nabothian cysts as a cause of post ablative I-131 uptake should be considered.
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