The radiological reports of 629 consecutive PET CT examinations were reviewed and all clinically relevant incidental findings were recorded. In particular we review 2nd primary lesions, thyroid and adrenal lesions, aortic aneurysms and other incidental findings.
2nd primary malignancy
Discovery of a 2nd primary malignancy is probably the most important incidental finding on a PET CT scan. The records of all patients with scans showing a possible 2nd primary malignancy were audited.
Colon
All patients scans with focal colonic FDG uptake were audited. 8 cases of bowel adenocarcinoma and 6 cases with dysplastic polyps were identified. Figures 10 and 11 show a case of a patient with T2, N0, M0 lung cancer who also had a T2, N0, M0 caecal tumour. Both of these lesions were resected.
Other confirmed second primary malignancies discovered in our series of 629 consecutive scans were:
Pleomorphic adenoma of the parotid gland (Figures 4-9),
Follicular carcinoma of the thyroid,
Non small cell lung cancer,
Synchronous primary lung cancer,
Follicular lymphoma (Figures 12-15)
Many other cases of suspected second malignancies were identified, however histological diagnosis was not obtained in the majority of patients. This is due to the degree of underlying disease and the need to balance further investigations with a patient's prognosis.
Aortic Aneurysms
Aortic aneurysms are frequently seen, this is in common with standard abdominal CT. 25 abdominal aortic aneurysms greater than 3 cm were identified - equivalent to a 4.0% incidence. (Figures 1-3). One thoracic aneurysm measuring 4.9cm and 3 common iliac aneurysms were also highlighted.
Thyroid Gland
Thyroid gland abnormalities are also common. These can be broadly divided into 3 types:
Diffuse thyroid uptake in the absence of CT abnormality (Figures 26-28)
Non FDG avid low attenuation nodules (Figures 23-25)
FDG avid thyroid lesions (Figures 29 and 30, anaplastic thyroid Ca)
A study by Ja Seong Bae et al concluded 'This study suggests that incidentally found thyroid lesions by FDG-PET/CT, especially a focal FDG uptake and a high SUV, have a high risk of thyroid malignancy. Further diagnostic work-up is needed in these cases.1'
Oesophageal Uptake
Incidental case of a patient with diffuse oesophageal uptake with a background on Epidermolysis Bullosa and metastatic squamous cell carcinoma (Figures 31 and 32).