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Primary Thyroid Lymphoma: External Beam Radiation Therapy Induced Thyroiditis Mimics Residual Disease on Serial 18F-FDG PET/CT Imaging


  • William Makis
  • Anthony Ciarallo
  • Stephan Probst

Received Date: 31.12.2016 Accepted Date: 15.10.2017 Mol Imaging Radionucl Ther 2018;27(1):41-47

A 67-year-old female patient with no prior history of benign thyroid disease was diagnosed with primary thyroid lymphoma and was staged with 18F-fluoro-2-deoxy-D-glucose (18F-FDG) positron emission tomography/computed tomography (PET/CT). She was treated with chemotherapy and external beam radiation therapy, and a follow-up PET/CT showed significant reduction in the size of the thyroid lymphoma with persistent intense 18F-FDG uptake, which was interpreted as partial response to therapy. However, two subsequent PET/CT studies showed no change in the persistent intense 18F-FDG uptake in the thyroid and a biopsy confirmed the presence of thyroiditis with no evidence of residual lymphoma. Follow-up PET/CTs performed over the subsequent three years showed stable intensely 18F-FDG avid thyroiditis with no evidence of lymphoma recurrence. We present the imaging characteristics of a long term radiation treatment induced thyroiditis mimicking 18F-FDG avid residual disease on PET/CT.

Keywords: Thyroid lymphoma,thyroiditis,pitfall,artifact,18F-FDG,PET


Informed Consent: All subjects in the study gave written informed consent or the institutional review board waived the need to obtain informed consent.

Peer-review: Externally peer-reviewed.

Authorship Contributions

Surgical and Medical Practices: W.M., A.C., S.P., Concept: W.M., Design: W.M., Data Collection or Processing: W.M., A.C., S.P., Analysis or Interpretation: W.M., A.C., S.P., Literature Search: W.M., A.C., S.P., Writing: W.M.

Conflict of Interest: No conflict of interest was declared by the authors.

Financial Disclosure: The authors declared that this study received no financial support.

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