title: Fluorodeoxyglucose positron emission tomography in primary thyroid lymphoma with coexisting lymphocytic thyroiditis.
abstract: BACKGROUND
  Primary thyroid lymphoma is an uncommon neoplasm frequently associated with lymphocytic thyroiditis (LT). Once the pathologic diagnosis of primary thyroid lymphoma is established, imaging plays an important role in tumor staging and evaluating treatment response. The present case discusses the role of fluorodeoxyglucose positron emission tomography (18F-FDG PET)/computed tomography (CT) in this clinical setting along with the potential diagnostic challenges.
  
  
  METHODS
  A 44-year-old man with a history of LT and hypothyroidism presented with an enlarging goiter. Initial imaging evaluation showed markedly enlarged gland with bilateral cervical and mediastinal adenopathy. Histopathologic evaluation confirmed the diagnosis of primary thyroid lymphoma on a background of LT. An 18F-FDG PET/CT revealed increased uptake in the gland and lymph nodes. Follow-up 18F-FDG PET/CT after chemotherapy showed interval decrease in FDG uptake in the thyroid gland associated with interval decrease in the size and metabolic activity of the cervical and superior mediastinal lymph nodes.
  
  
  CONCLUSIONS
  The frequent association of LT with primary thyroid lymphoma and the overlap of their clinical and pathologic findings pose a significant diagnostic challenge. While other imaging techniques are helpful in evaluating anatomic local and regional extent of primary thyroid lymphoma, 18F-FDG PET/CT can be of an added value in evaluating its metabolic activity and detecting regional and distant disease as well as in assessing response to treatment.
authors.affiliation: Division of Nuclear Medicine, Department of Radiology, University of Michigan Health Systems, Ann Arbor, Michigan 48109-5028, USA. marabi@med.umich.edu
authors.forename: Mohammad
authors.initials: M
authors.lastname: Arabi
authors.forename: Ryan
authors.initials: R
authors.lastname: Dvorak
authors.forename: Lauren B
authors.initials: LB
authors.lastname: Smith
authors.forename: Lisa
authors.initials: L
authors.lastname: Kujawski
authors.forename: Milton D
authors.initials: MD
authors.lastname: Gross
mesh_terms: D000328:Adult; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D015897:Comorbidity; D003520:Cyclophosphamide / Q000627:therapeutic use; D003937:Diagnosis, Differential; D004317:Doxorubicin / Q000627:therapeutic use; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008223:Lymphoma / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000453:epidemiology*; D008297:Male; D064847:Multimodal Imaging; D009367:Neoplasm Staging; D049268:Positron-Emission Tomography; D011241:Prednisone / Q000627:therapeutic use; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000453:epidemiology*; D013967:Thyroiditis, Autoimmune / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000453:epidemiology*; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D014750:Vincristine / Q000627:therapeutic use
chemical_list: D019788:Fluorodeoxyglucose F18; D014750:Vincristine; D004317:Doxorubicin; D003520:Cyclophosphamide; D011241:Prednisone