Primary Functioning Neuroendocrine Tumor of the Appendix with Hypoglycemia Syndrome: A Case Report and Review of Neuroendocrine Tumors

Abstract

Introduction: Primary neuroendocrine tumors (NETs) of the appendix are uncommon, but when present are usually not hyperfunctioning. This case represents an extraordinarily rare primary hyperfunctioning NET of the appendix with a clinical presentation of symptomatic hypoglycemia in an otherwise healthy man.

Case presentation: A previously healthy 34-year-old man was found to be symptomatically hypoglycemic in early 2018. After the workup, the apparent explanation was a tumor in his midappendix, for which he was referred to our surgical oncology service for resection. The patient's clinical course is described in detail, including imaging, as well as surgical and pathologic descriptions of the appendiceal NET.

Discussion: A literature review demonstrates no other case series or reports of a primary hyperfunctioning NET of the appendix presenting with hypoglycemic crisis. The symptoms of tumor-induced hypoglycemia more typically arise with islet cell tumors, such as pancreatic NETs or insulinomas. We believe this case represents a nonislet cell tumor-induced hypoglycemia. This patient's elevated serum proinsulin level preoperatively implies secretion of proinsulin by the tumor. However, tumor-induced hypoglycemia caused by proinsulin has been described previously only in pancreatic tumors. This unique case adds knowledge to the possible glycemic endocrine effects of nonpancreatic NETs, specifically those that arise primarily in the appendix.

Figure 1

Computed tomography scan of abdomen with contrast enhancement showing 1.27-cm mass in midappendix.

Figure 2

Gallium dotatate Ga 68-enhanced scan of abdomen in transverse view demonstrating hyperactive, 1.3-cm nodule in midappendix.

Figure 3

Gallium dotatate 68 Ga-enhanced scan of body in coronal view. Hyperactive, 1.3-cm nodule in midappendix shows no evidence of metastatic disease or mass in pancreas or duodenum.

Figure 4

Surgical margins negative for tumor invasion (hematoxylin-eosin stain, 100× magnification).

Figure 5

Appendiceal tumor (hematoxylin-eosin stain, 200× magnification).

Figure 6

Timeline of the case. CC = chief complaint; CT = computed tomography; EUS = endoscopic ultrasonography; GI = gastrointestinal; IM = intramuscular; OR = Operating Room; PET = positron emission tomography; w/wo = with and without.