Table 1.

Normal biodistribution of prostate-membrane-specific antigen (PSMA) and somatostatin receptor (SSTR)-targeting positron emission tomography imaging agents as well as important pitfalls, that may be seen with both imaging probes

Imaging agents	PSMA	SSTR
Normal biodistribution	Lacrimal glands Salivary glands Liver Spleen Kidneys Small bowel Ganglia Radiotracer excretion via urinary tract [18, 19]	Pituitary gland Major salivary glands Thyroid Adrenal glands Liver Spleen Pancreatic uncinate process Splenosis, splenunculi Radiotracer excretion via urinary tract [20]
Important pitfalls	Benign pathologies mimicking PCa  Granulomatous diseases: sarcoidosis, Wegner’s granulomatous, tuberculosis [24–27] Benign bone diseases  Fibrous dysplasia, healing fractures, Paget’s disease [28–30] Benign tumors of neurogenic origins  Schwannomas, peripheral nerve sheath tumors, or meningiomas [31–33] Hemangiomas [34] and benign soft-tissue pathologies  Desmoid tumors, intramuscular myxoma, and pseudo-angiomatous stromal hyperplasia [35–37] PSMA-avid tumor entities other than PCa  Follicular thyroid carcinoma, pancreatic NET, renal cell carcinoma, radio-iodine refractory thyroid carcinoma [38–40, 42]	Inflammatory diseases  Large arteries, sarcoidosis, arthero-sclerotic plaques [47–49] Degenerative bone structures [20] Vertebral hemangioma [50] Rare NET tumors  Medullary thyroid carcinoma [51]  Paraganglioma and pheochromocytoma [52] Non-NET tumors  Meningioma, primary central nervous system lymphoma, breast cancer, papillary thyroid cancer [54–57]

The normal biodistribution of both imaging agents can also be appreciated in Fig. 1

PCa prostate cancer, NET neuroendocrine tumors