Metastatic Non-Functional Pancreatic Neuroendocrine Tumor in a Patient With a Pathogenic TSC1 Mutation

Abstract

Abstract Introduction: Tuberous sclerosis complex (TSC) is an autosomal dominant multisystem disorder caused by mutations in two tumor suppressor genes (TSC1 and TSC2) encoding proteins critical in cell growth and proliferation and is associated with an increased risk for benign and malignant tumors. Pancreatic neuroendocrine tumors (PNET) occur in 1.5-1.8% of patients with TSC. They have been primarily reported in TSC2, with only a few cases in the context of TSC1. We describe a non-functional metastatic PNET in a patient with a known pathogenic TSC1 mutation. Case Description: A 49-year old female with a past medical history of bipolar disease, a family history of TSC1 in a daughter, a known pathologic TSC1 mutation (c.2356C>T), and previous history of renal cell carcinoma (RCC) was evaluated for a pancreatic lesion with likely liver metastases. Two years prior to the presentation, a 10 mm pancreatic lesion was initially noted on the CT scan during a renal mass evaluation. Nephrectomy confirmed the RCC. Two years later, surveillance imaging revealed two new lesions in the liver, and the pancreatic lesion had enlarged to 1.3 cm. She denied symptoms suggestive of a functional PNET, and her physical exam was unremarkable. Gallium-68 dotatate (GA-68) PET/CT scan demonstrated avid lesions of both the pancreatic tail and left hepatic lobe. Biopsy of the 3 cm liver mass revealed a metastatic high-grade neuroendocrine carcinoma (mib-1 proliferation index of 15%) favoring a primary PNET. Immunohistochemical stains were positive for chromogranin A, synaptophysin, EMA, PAX 8, CK 20, and villin. Stains for CA 19-9 and CK 7 were negative. Biochemical testing suggested that the PNET was non-functional. Specifically, serum concentrations of gastrin, somatostatin, glucagon, glucose, C-peptide, proinsulin, pancreatic polypeptide, chromogranin A, and vascular endothelial growth factor were within normal limits. The patient underwent distal pancreatectomy and resection of the liver mass. Pathological specimens confirmed the diagnosis of a PNET. The patient remained asymptomatic and was monitored regularly with MRI and GA-68 PET/CT scans without further evidence of the disease for 1.5 years. Conclusions: We conclude that this patient harboring a c.2356C>T TSC1 mutation developed a non-functional metastatic PNET. PNET is a likely component of TSC1.