Metachronous Appearance of a Pancreatic Neuroendocrine Tumor and Colonic Adenocarcinoma: Case Report

Abstract

Neuroendocrine tumors (NET) are relatively rare but their co-existence with a metachronous secondary primary malignancy (SPM) is even more rare. However, more cases of patients with both tumor types are being reported. In fact, rates of SPMs are up to 55% in neuroendocrine tumors. We present a case of a 58 year-old male with a history of a non-functional pancreatic neuroendocrine tumor (PEN) status-post robotic enucleation in 2013, bladder cancer status-post resection, diabetes mellitus, hypertension, diverticulosis, and asthma who was transferred from an outside hospital for further evaluation of a possible colonic obstruction. Initial computed tomography (CT) imaging showed a posterior extension of the inflamed colon with the appearance of a sinus tract that abutted the pancreatic tail and inferior splenic capsule. Given concern for recurrent PEN, he underwent flexible sigmoidoscopy where a circumferential, partially occluded colonic mass was found starting around the proximal descending colon across the splenic flexure. Endoscopic ultrasound (EUS) showed a 3.25 cm infiltrating hypoechoic lesion with areas of hyperechogenicity was seen arising from the tail of the pancreas. The mass appeared to be infiltrating into the adjacent colon as well as appeared to compress the splenic vein. Biopsies taken during flexible sigmoidoscopy revealed a mix of at-least high-grade dysplastic glandular epithelium, benign pancreatic acinar tissue, and gastric foveolar epithelial contaminants. Immunoperoxidase stains were performed and revealed overlapping of CK7/CK20 immunoprofiles of pancreatic mucinous and colonic mucinous neoplasms. Thus, the biopsy was inconclusive as to the primary origin of the mass. The patient underwent a left hemicolectomy, distal pancreatectomy, splenectomy and partial left adrenalectomy were performed. Surgical pathology showed findings of stage IIC T4bN0M0 low-grade mucinous colonic adenocarcinoma with positive perinephric margins. He decided to proceed with chemotherapy. It is recommended that patients diagnosed with NET should undergo investigation for concomitant SPM. Per literature review, a majority of the SPMs appear to be in the gastrointestinal tract suggesting that endoscopic evaluation in addition to CT imaging may be of use. However, further studies are required to assess the utility of SPM screening as well as to clarify the mechanism of carcinogenesis between neuroendocrine tumors and secondary primary malignancies.Figure: Initial CT abdomen and pelvis without contrast shows inflamed colonic mass, suggesting malignancy in conjunction with patient's presenting symptoms.Figure: Initial CT abdomen and pelvis without contrast shows posterior extension of the inflamed colon with the appearance of a sinus tract that abutts the pancreatic tail and inferior splenic capsule.Table: Table. Literature review of cases of neuroendocrine tumor-associated secondary primary malignancies