Diffuse Pancreatic Neuroendocrine Tumor: A Rare Presentation

A 31-year-old female presented to the emergency department with abdominal pain, nausea, and vomiting. Computed tomography (CT) scan of the abdomen showed diffuse enlargement of the pancreas with a hypervascular focus in the tail of the pancreas, suspicious for a neuroendocrine tumor. An In-111 pentetreotide scan was performed, which showed diffuse increased uptake in an enlarged pancreas [Figure 1a and b]. The normal distribution is seen in the spleen, liver, kidneys, and the urinary bladder. No focal lesions or metastatic disease was seen. Corresponding transaxial image [Figure 1c] from the contrast-enhanced CT scan of the abdomen and pelvis shows diffusely enlarged pancreatic body and tail (dashed white arrows) and a focal hypervascular lesion in the tail of the pancreas. A distal pancreatectomy was performed, which showed diffuse involvement of the pancreas with a neuroendocrine tumor [Figure 1d]. A completion total pancreatectomy (Whipple's procedure) was later performed which showed a low-grade diffuse pancreatic neuroendocrine tumor. There was a local invasion of the duodenum with negative margins and no evidence of nodal metastasis. The neuroendocrine differentiation was confirmed on immunohistochemical staining with markers such as chromogranin A [Figure 1e] and Synaptophysin (not shown). Ki67 index (a marker of cellular proliferation) was <2%, suggesting a low-grade tumor.

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Figure 1 Anterior and posterior whole body images (a and b respectively) acquired 6 hrs after IV administration of 222 MBq (6.0 mCi) of In-111 pentetreotide. Diffuse increased uptake is seen in the enlarged pancreas involving the head, body and the tail of the pancreas. On the posterior whole-body image, a focal attenuation artifact is seen in the midline, from the spine. (c) Transaxial contrast-enhanced computed tomography scan image of the abdomen and pelvis shows diffusely enlarged pancreatic body and tail (dashed white arrows) and a focal hypervascular lesion in the tail of the pancreas. (d) is the (H and E × 40) of the tumor showing nests of polygonal tumor cells which typically have stippled salt-and-pepper chromatin and eosinophilic granular cytoplasm. (e) immunohistochemical staining with markers such as Chromogranin A shows neuroendocrine differentiation

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Pancreatic neuroendocrine tumors are rare tumors that are typically classified as functional versus nonfunctional (based on laboratory testing) and differentiated versus de-differentiated (based on the immunohistochemistry).[123] They usually present as a focal hypervascular mass on CT imaging, hyperdense on the arterial, and portal venous phases.[456] Since these tumors are neuroendocrine in origin, they express somatostatin receptors on their cell membranes, a binding site for In-111 pentetreotide. In-111 pentetreotide imaging is performed for confirmation (of neuroendocrine origin), whole body staging, and assessing response to treatment.[789] Pancreatic neuroendocrine tumors and metastasis are seen as foci of increased uptake on whole-body imaging with In-111 pentetreotide.[9] Single-photon emission computed tomography (CT) imaging has been reported to be useful for anatomical localization of metastatic disease when using In-111 pentetreotide.[10] Diffuse pancreatic infiltration with neuroendocrine tumor is a rare presentation, previously reported once on anatomic imaging.[611] Diffuse uptake of In-111 pentetreotide has previously been reported in the lungs,[1213] but diffuse uptake in the pancreas from a neuroendocrine tumor has not been reported previously. In conclusion, this case highlights a rare presentation of a well-differentiated, low-grade neuroendocrine tumor as the diffuse involvement of the pancreas, with local invasion, but no nodal or distant metastasis.