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Radioiodine uptake in inactive pulmonary tuberculosis.
S M Bakheet1, M M Hammami, J Powe
1Department of Radiology, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia.
European Journal of Nuclear Medicine
|June 17, 1999
Summary
Radioiodine uptake in the lungs of thyroid cancer patients can mimic metastases due to inflammation or infection, particularly in those with a history of tuberculosis. Further investigation is crucial to differentiate true metastases from false positives.
Area of Science:
- Nuclear Medicine
- Oncology
- Pulmonology
Background:
- Radioiodine (radioactive iodine) can accumulate in areas of inflammation or infection within the lungs.
- Thyroid cancer patients with a history of pulmonary tuberculosis may exhibit unusual radioiodine uptake patterns.
- Differentiating true pulmonary metastases from false-positive findings is critical for accurate diagnosis and treatment.
Purpose of the Study:
- To investigate the causes of false-positive radioiodine uptake in the lungs of thyroid cancer patients.
- To analyze the characteristics of radioiodine uptake in patients with a history of pulmonary tuberculosis.
- To highlight the importance of considering pulmonary infection/inflammation as a cause of false-positive radioiodine uptake.
Main Methods:
- Review of six thyroid cancer patients with a history of treated pulmonary tuberculosis.
- Analysis of iodine-123 diagnostic scans to identify and characterize radioiodine uptake foci.
- Correlation of imaging findings with clinical symptoms, chest radiographs, thyroid hormone levels, and gallium-67 uptake.
Main Results:
- Eight foci of radioiodine uptake were observed in six patients.
- Three foci were focal and indistinguishable from metastases; five were nonsegmental, linear, or lobar, suggesting false positives.
- Uptake patterns were variable, non-persistent, and less extensive than fibrocystic changes; thyroid hormone levels and gallium-67 uptake did not correlate.
- No evidence of recurrent thyroid cancer or active tuberculosis was found.
Conclusions:
- Pulmonary inflammation/infection, including tuberculosis sequelae, can cause false-positive radioiodine uptake mimicking thyroid cancer metastases.
- Various lung conditions like bronchiectasis, bronchitis, and fungal infections can lead to abnormal radioiodine chest uptake.
- Clinicians must consider non-malignant causes of radioiodine lung uptake in thyroid cancer patients to avoid misdiagnosis of pulmonary metastases.