Pulmonary Aspergilloma Mimicking Metastasis from Papillary Thyroid Cancer

Background: Whole-body scans (WBSs) based on diagnostic or therapeutic doses of I-131 can visualize metastatic lesions in thyroid cancer patients who have undergone total thyroidectomy. However, a variety of unusual lesions may cause false-positive results, and therefore, careful evaluation of abnormal scans is imperative to avoid unnecessary surgical removal or high-dose radioiodine treatment. Here, we report a patient with pulmonary aspergilloma mimicking metastasis of thyroid cancer on WBS. Summary: A 53-year-old woman with papillary thyroid cancer stage III (T1N1aM0) who had undergone total thyroidectomy and 150 mCi of radioiodine treatment for remnant ablation was found to have focal intense radioiodine accumulation in the left lung field by WBS, suggestive of pulmonary metastasis, at 5 days after I-131 administration. Whole-body F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) and Tc-99m methoxyisobutyl isonitrile scans showed no remarkable tracer accumulation at the pulmonary nodule. An enhanced chest CT scan demonstrated a nonenhancing pulmonary nodule with an air-crescent sign suggestive of pulmonary fungus ball. A subsequent blood test for precipitating antibodies to Aspergillus antigens produced a result of 29.9U/mL (reference range: 0-8 U/mL). The patient was clinically diagnosed as having pulmonary aspergilloma based on serologic test and radiologic imaging results. Conclusion: Extreme caution should be exercised when interpreting abnormal radioiodine WBS findings when the serum thyroglobulin is normal and imaging characteristics indicate a benign condition. Pulmonary aspergilloma is a cause of a false-positive lesion when radioiodine WBSs are performed.