HISTORY

63 year old woman initially presented with rectal bleeding and abdominal pain.  Initial evaluation included abdominal sonography, which demonstrated several hepatic masses, as well as colonoscopy, which demonstrated a well differentiated rectal adenocarcinoma.  One of the hepatic masses was biopsied, which demonstrated a well differentiated neuroendocrine tumor.

Subsequent computed tomographic imaging and somatostatin receptor scintigraphy, demonstrated two distinct populations of liver lesions. There were multiple low attenuation hepatic lesions with increased tracer accumulation, consistent with neuroendocrine hepatic metastases, which correspond to hyperenhancing lesions on the contrast enhanced CT examination. There were two large low-attenuation lesions which had less tracer accumulation than normal liver parenchyma, which correspond to hypoenhancing lesions on the contrast enhanced CT examination.  These studies also demonstrated a soft tissue mass, within the terminal ileum with increased tracer accumulation, which correspond to a hyperenhancing mass on the contrast enhanced CT examination.  This likely represents the primary neuroendocrine tumor.  Subsequent liver biopsy demonstrated well differentiated adenocarcinoma metastasis.

DISCUSSION

Octreotide scintigraphy is based on neuropeptide receptor imaging.  Somatostatin is a neuropolypeptide and somatostatin receptors are present in an increased density within several neuroendocrine tumors.  Neuroendocrine tumors include carcinoid, pancreatic islet cell neoplasms, pheochromocytomas, neuroblastomas, paragangliomas, pituitary adenomas, medullary carcinoma of the thyroid, and small-cell lung cancers.  While many of these lesions are well evaluated with octreotide scintigraphy, exceptions include insulinomas and medullary thyroid carcinoma.  Planar imaging enables visualization of the entire body, which can be useful in locating the primary neoplasm, as well as metastatic disease.  Single photon emission computed tomography - computed tomography can be useful for better localization.  Octreotide scintigraphy has a higher sensitivity for well differentiated tumors, secondary to increased somatostatin receptor density.  Therefore, visualization may indicate a more favorable diagnosis, given well differentiation, as well as patients are more likely to be candidates for octreotide therapy.