111In-Pentetreotide uptake in a follicular adenoma of the thyroid gland: a pitfall for 111In-Pentetreotide scintigraphy

A patient with suspicion of a neuroendocrine tumor of the pancreas underwent a somatostatin receptor scintigraphy using 111In-Pentetreotide. 111In-pentetreotide scintigraphy showed discrete uptake of the radiotracer in the head of the pancreas and focal uptake in the right upper thyroid lobe. Tracer uptake in the 24h planar image was higher compared to the 4h image, and decreased after 48 hours. Normal thyroid tissue and thyroid disorders, such as cancers, Hashimoto's thyroiditis, and adenomas often show increased uptake of 111In-pentetreotide resulting in a possible false positive interpretation in patients with neuroendocrine tumor. Adding a 48h planar image might contribute to the differential diagnosis between benign or malignant lesions, as in the present case where the uptake decreased in an adenoma after 48 hours.