Oncology Case 5

Oncology Case 5

Submitted by
Dr. Jasim Jaleel,
Assistant Professor,
Department of Nuclear Medicine,
Institute of Liver and Biliary Sciences, New Delhi, India.

A 67 year old male, case of multifocal hepatocellular carcinoma, underwent 18F-FDG PET/CT for baseline staging. In addition to the primary disease, PET/CT revealed an FDG avid hypodense nodule measuring 1.2 x 1.4 cm with a SUVmax 4.7, involving the mid and inferior pole of right lobe of thyroid gland. What should be the next line of management of thyroid nodule?

a) Advise a follow-up scan after 6 months.

b) Advise 99mTc-pertechnetate scan correlation.

c) Advise an ultrasonography and FNAC correlation

d) Advise an ultrasonography correlation.

e) Advise an FNAC correlation.

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Answer: c. Advice an ultrasonography and FNAC correlation

The incidence of thyroid incidentalomas on 18F- FDG PET/CT varies between 1% and 4% in most studies and up to 2.5% in a recently published meta-analysis (1-4). Focal FDG uptake in thyroid nodules is associated with an increased risk of malignancy (1). 2014 BTA guidelines classify FDG-avid nodules as high-risk nodules (5). The risk of malignancy in FDG-avid thyroid nodules is approximately 35%, and most are differentiated thyroid cancers (6). Studies and meta-analyses have shown that malignant nodules show higher SUVmax than benign nodules (1,4,7).

The 2014 BTA guidelines suggest that “nodules detected by PET-CT with focal FDG activity should be investigated with ultrasound and FNAC, unless disseminated disease is identified and the prognosis from an alternative malignancy would preclude further investigation” (5). The 2015 ATA guidelines states that “focal FDG uptake within a sonographically confirmed thyroid nodule conveys an increased risk of thyroid cancer, and fine needle aspiration is recommended for those nodules ≥ 1 cm” (8).

TSH measurement is advisable for all thyroid incidentalomas so that any coexisting thyroid dysfunction can be detected and treated appropriately. A low TSH level may indicate hyperthyroidism, which could be due to a functional thyroid nodule that can be established using thyroid 99m technetium pertechnetate scintigraphy. Functional thyroid nodules are rarely malignant (9).


  1. Soelberg KK, Bonnema SJ, Brix TH, Hegedüs L. Risk of malignancy in thyroid incidentalomas detected by 18F-fluorodeoxyglucose positron emission tomography. A systematic review. Thyroid. 2012; 22: 918-925.
  2. Chen YK, Ding HJ, Chen KT, et al. Prevalence and risk of cancer of focal thyroid incidentaloma identified by 18F-fluorodeoxyglucose positron emission tomography for cancer screening in healthy subjects. Anticancer Res. 2005; 25(2B): 1421-1426.
  3. Thuillier P, Roudaut N, Crouzeix G, et al. Malignancy rate of focal thyroid incidentaloma detected by FDG PET-CT: results of a prospective cohort study. Endocr Connect. 2017; 6(6): 413-421.
  4. Bertagna F, Treglia G, Piccardo A, Giubbini R. Diagnostic and clinical significance of F-18-FDG-PET/CT thyroid incidentalomas. J ClinEndocrinolMetab. 2012; 97(11): 3866-3875.
  5. Perros P, Colley S, Boelaert K, et al. British Thyroid Association Guidelines for the management of thyroid cancer. ClinEndocrinol. 2014; 81(suppl 1): 1-122.
  6. Treglia G, Bertagna F, Sadeghi R, Verburg FA, Ceriani L, Giovanella L. Focal thyroid incidental uptake detected by ¹⁸F-fluorodeoxyglucose positron emission tomography. Nuklearmedizin. 2013; 52(4): 130-136.
  7. Pathak KA, Goertzen AL, Nason RW, Klonisch T, Leslie WD. A prospective cohort study to assess the role of FDG-PET in differentiating benign and malignant follicular neoplasms. Ann Med Surg. 2016; 12: 27-31.
  8. Haugen BR, Alexander EK, Bible KC, et al. 2015 American Thyroid Association Management Guidelines for adult patients with thyroid nodules and differentiated thyroid cancer: the American Thyroid Association Guidelines Task Force on thyroid nodules and differentiated thyroid cancer. Thyroid. 2016; 26(1): 1-133.
  9. Wadsley J, Balasubramanian SP, Madani G, et al. Consensus statement on the management of incidentally discovered FDG avid thyroid nodules in patients being investigated for other cancers. ClinEndocrinol. 2023. doi:10.1111/cen.14905