Cadherin 1 germline mutation co-occurs with medullary thyroid cancer and choroid plexus papilloma: A case report and review of literature.

Background: We describe the case of a 23-year-old woman with a history of medullary thyroid cancer (MTC) who presented with a choroid plexus papilloma (CPP) and review the literature regarding the co-occurrence of these two pathologies. Case Description: A 23-year-old woman with a history of MTC treated with thyroidectomy 3 months prior was referred to neurosurgery with an incidental fourth ventricular mass found on prior imaging of her neck. She presented to the clinic with intermittent headaches and underwent MRI which demonstrated a hyperintense, heterogeneously enhancing lobular mass at the obex of the fourth ventricle. She underwent suboccipital craniotomy and C1 laminectomy for resection of tumor with pathology revealing CPP. No somatic mutations unique to the tumor were found after targeted exome sequencing and tumor-normal paired analyses. Interestingly, germline sequencing reveals a mutation in the tumor suppressor Cadherin 1(CDH1). Conclusion: Mutations in CDH1 may play a role in an underlying predisposition toward the development of MTC and CPP. Current literature identifies no definitive connection between MTC and CPP, though future studies may suggest the role of this gene beyond a predisposition to gastric and breast cancer.