In which of the following sites does 111 pentetreotide typically NOT localize?

111 pentetreotide is a radiopharmaceutical used primarily in nuclear medicine for imaging neuroendocrine tumors. It is a somatostatin analog that binds to somatostatin receptors, which are often overexpressed in certain tumors, particularly neuroendocrine tumors.

The reason salivary glands are noted as a site where pentetreotide typically does not localize lies in the pattern of somatostatin receptor expression. While pentetreotide can accumulate in various organs that have a high density of somatostatin receptors, the salivary glands are not a common site for such significant receptor expression. Consequently, imaging may show little to no uptake in the salivary glands compared to other organs.

In contrast, the pituitary glands, spleen, and thyroid gland may have varying degrees of somatostatin receptor expression. The pituitary gland is known to have somatostatin receptors and can show significant uptake, particularly in patients with pituitary adenomas. The spleen also has a certain level of somatostatin receptor expression, and while uptake may not always be significant, it is more typical than in the salivary glands. Similarly, the thyroid gland can express somatostatin receptors, although