A 71-year-old man, with follicular variant of papillary thyroid carcinoma, underwent total thyroidectomy and neck dissection followed by radioiodine ablation 2 years ago. His post-therapy whole body scan did not show any concentration except in the neck region. Subsequently, he was symptom-free for 2 years. He, recently, presented with abdominal discomfort and an ultrasound showed multiple, ill-defined, solid, irregular space-occupying lesions in the liver. Considering that (i) liver involvement from differentiated thyroid carcinoma is relatively uncommon; (ii) controlled serum thyroglobulin value was not consistent with thyroid primary; and (iii) the patient was on levothyroxine therapy, a whole body FDG-PET/CT (without contrast) was done before an 131I scan and showed intense FDG uptake in multiple hypodense lesions in the liver (largest measuring 11.4x4.6 cm and SUV max 20.03; Figs 1a and 1b). Intense FDG uptake was also seen in the lower oesophagus at the gastro-oesophageal junction extending into the proximal stomach (SUV max 11.87) along with an enlarged FDG avid gastrohepatic lymph node (2.1x2.3 cm) with SUV max 15.17. An endoscopic biopsy showed that the growth was a poorly differentiated adenocarcinoma (grade 3) of the oesophagus.
Detection of an unsuspected second primary (either synchronous or metachronous) has been an important aspect of whole body FDG-PET/CT. This could be either in unsuspected incidentalomas or in the clinical oncology setting where metastases are not likely to be from the known primary and the tumour marker is normal/undetected. This could be useful because second primary cancers are the sixth commonest malignancy after those of the skin, prostate, breast, lung and colorectal carcinoma.1,2