64 year old male with history of stage 4 prostate cancer status post radiosurgery and hormonal therapy in remission for 6 months presented with 1 month of left upper quadrant and epigastric pain associated with nausea, anorexia and unintentional 15 lb weight loss within 8 months. His PSA level was significantly elevated at 184 mg/dL from previous 0.4 mg/dL with elevated lipase of 402 U/L. Ca 19-9 was also elevated at 45.1 U/mL. On exam, he had no jaundice, scleral icterus or palpable mass, but did complain of tenderness in LUQ of abdomen. An ultrasound showed a pancreatic mass. CT scan identified multiple hypoenhancing pancreatic lesions, liver and adrenal metastases and peritoneal carcinomatosis with portal vein thrombosis. EUS showed large irregular pancreatic mass in head of pancreas. Pathology of lymph node and mass identified poorly differentiated carcinoma. Immunostain showed tumor nuclei strongly positive for androgen receptors, but negative stains for PSA and prostein. Panel reflected possible prostatic origin.
Prostate specific antigen (PSA) is a frequently used marker for prostate cancer. It is a glycoprotein exhibiting serine protease activity and very specific for prostatic epithelial cells. Several case reports in literature show nonprostatic expression of PSA. PSA-like immunoreactivity has been identified in other tissues such as breast milk, breast tumors and the sera of various cancers including the pancreas. Limited data exists regarding PSA expression in the pancreas. The pancreas is also considered a rare site for prostate cancer metastasis. One autopsy study looked at 1,589 patients with metastatic prostate cancer and only 1.4% showed metastasis to the pancreas. Based on pathology, he possibly has metastasis to pancreas, but this is undiagnostic. Histology of prostate cancer would be beneficial to further evaluate. Interestingly, he appeared to have a primary pancreatic tumor on imaging. Pathology is important as patients can clinically and radiologically mimic primary tumors like in this case. Clinicians should distinguish primary from secondary tumors as management can vary. Primary pancreatic cancer is often fatal and aggressive whereas isolated metastases may have improved outcomes with surgery.
In this case, we report a man with elevated PSA and pancreatic adenocarcinoma. Although PSA is most commonly associated with prostate cancer, clinicians should consider other causes of elevated PSA in patients outside of the prostate such as the pancreas.