Introduction: Choline is a precursor of phospholipids which is integrated into the cell membrane during cell proliferation, when labelled with 18-Fluorine (18F), has utility in the imaging of cancer, primarily prostate cancer. Serendipitously, the tracer was recognised to show uptake in parathyroid adenoma in 2013 by Quak et al when imaging a patient with concurrent primary hyperparathyroidism and prostate cancer.[i] We describe a case of suspected parathyroid carcinoma, and will outline the utility and potential pitfalls of PET imaging.
Case Report: A 67 year old male was incidentally found to be hypercalcemic (corrected calcium 3.28 mmol/L) on routine blood investigations. Biochemistry confirmed primary hyperparathyroidism with a PTH of 113.7 (1.6 – 6.9) pmol/L. Neck ultrasound revealed a 29mm hypo echoic heterogeneous vascular lesion with a central cystic component deep to the right thyroid lobe. Imaging and biochemical characteristics were suspicious for parathyroid carcinoma.[ii]
For anatomical correlation a 4dCT was arranged, the mass abutted the oesophagus and two tiny lymph nodes directly inferior to the mass measuring 3-4mm were identified.
For staging purposes, whole body imaging was performed using 18F-Fluorocholine PET-CT and 18F-FDG PET-CT. The neck mass showed intense Fluorocholine avidity and minimal FDG uptake. A left iliac bone lesion was detected which showed both intense Fluorocholine and FDG avidity. This correlated to a subtle, 1cm, bone lucency on attenuation correction CT. The small lymph nodes evident on 4dCT were neither Fluorocholine nor FDG avid.
The patient went onto neck surgery, PTH normalised (2.8 pmol/L) 3hours following surgery.
Discussion: Given that 18F-Fluorocholine is not specific for parathyroid tumour and the normalization of PTH following surgery, a biopsy with PTH titre of the left iliac lesion is planned. Histopathological findings will be outlined in full at the conference.