Objective: We report the presentation and novel therapy of a calcitonin-secreting pancreatic neuroendocrine tumor (PNET) and review the literature on this unusual neoplasm.
Methods: We cite the history of a 38-year-old male who presented with fatigue, weight loss, and diarrhea and was found to have a pancreatic head mass on cross-sectional imaging, as well as liver metastases.
Results: The patient's laboratory evaluation was notable for a >100-fold elevation of the peptide hormone calcitonin in serum. As calcitonin is typically secreted by thyroid C-cells, hypercalcitoninemia is considered a marker for medullary thyroid cancer (MTC) or C-cell hyperplasia, but it may be present in several physiologic or pathologic conditions or may be ectopically secreted in rare PNETs. An octreotide scan confirmed the presence of somatostatin (SST) receptors on the pancreatic mass and liver metastases, leading to the diagnosis of a calcitonin-secreting PNET. We initiated treatment with long-acting SST analogs and peptide receptor radionuclide therapy (90Yttrium-DOTATOC) and achieved disease regression while maintaining a high quality of life.
Conclusion: Functional PNETs that secrete calcitonin are exceedingly rare, but they are important to consider in the differential diagnosis of nonthyroid-mediated hypercalcitonemia or pancreatic tumors that present with diarrhea, as the management differs markedly from both MTC and other pancreatic malignancies.