Incidental focal thyroid uptake on ¹⁸F-Choline PET-CT: need to rule out thyroid cancer

Excerpt

A 65-year-old man with a history of prostate cancer was referred for ¹⁸F-Choline Positron Emission Tomography with Computed Tomography (PET-CT) to explore a rising prostate-specific antigen level at 7 ng/ml. No ¹⁸F-Choline focus suggestive of prostate cancer recurrence was evidenced. A moderate ¹⁸F-Choline uptake (SUVmax = 4.1) was incidentally reported at the lower part of the left thyroid lobe (Fig. 1a, b). Ultrasound (US) examination depicted a 24-mm hypoechoic left thyroid nodule (Fig. 1c) with both intranodular and perinodular vascular signals on color Doppler examination (Thyroid Imaging Reporting and Data System score 4A). Serum Thyrotropin (TSH) level was 1.86 mUI/l (0.27–4.2). This nodule was cold on the ^99mTc thyroid scan. US guided fine-needle aspiration cytology reported atypia of undetermined significance (scored Bethesda III). Thyroid surgery was proposed and left lobectomy was performed. Pathology revealed a 2-cm follicular variant of papillary thyroid carcinoma (PTC) (Fig. 1d). The lesion was scored pT1bNxM0 (TNM classification, 8th edition)¹ and active surveillance was decided by multidisciplinary staff. After a 2-year follow-up period, the patient still presents an excellent response with a thyroglobulin (Tg) level at 2.5 ng/ml, no Tg antibody and a normal neck US.

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