False-positive octreotide scan due to pulmonary infection
Indium- 111 Octreotide scintigraphy is a useful investigation in the diagnosis and staging of carcinoid syndrome and other neuroendocrine malignancies. Tumours with large numbers of somatostatin receptors can be accurately imaged and this can be useful in guiding treatment. Although uncommon false-positive studies have been reported and often the cause is unexplained but assumed to be due to a high number of somatostatin receptors in other pathology. A 58-year-old woman was referred for investigation of flushing and an elevated 5HIAA level with a presumed diagnosis of carcinoid syndrome. An indium 111 octreotide study was performed and planar and tomographic images were obtained up to 48 hours following the administration of tracer. Planar and tomographic images demonstrated increased uptake in the right lung apex and a CT scan was performed to further evaluate this region as a possible site of carcinoid tumour. The CT scan demonstrated an area of consolidation in the right lung apex and fused images confirmed this region to be the area of increased uptake on the octreotide scan. Pneumonia as a cause of false-positive indium 111 octreotide uptake has previously been reported 1 however this case again confirms the need to correlate scan results with the patients clinical status to avoid false-positive results and also confirms the usefulness of fusion imaging (or hybrid imaging on SPECT CT cameras).