Multiple sclerosis, human herpesvirus 4 and thyroid collision tumor: A case report

The role of interferon β-1b (IFNβ-1b), used for multiple sclerosis (MS) therapy, in cancer occurrence is uncertain. There is evidence supporting the role of human herpesvirus 4 [Epstein-Barr virus (EBV)] in thyroid cancer and MS. Simultaneous occurrence of papillary and medullary carcinomas is rare, and its association with MS in a young woman raises questions. A 46-year-old female patient was diagnosed with relapsing-remitting multiple sclerosis in 2008. In 2018, cervical MRI detected a thyroid nodule with right cervical adenopathy. Her thyroid function was normal, but increased calcitonin levels were found (70.53 pg/ml; normal value