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: <9.82 pg/ml). EBV serology tested positive. Paraclinical studies ruled out multiple endocrine neoplasia syndrome. Whole thyroid resection with whole cervical lymph node dissection was performed. To our knowledge, this is the first case that describes an association between MS and thyroid collision tumors. Histological examination ascertained both papillary and medullary thyroid cancer. After surgery, the calcitonin level normalized, and the patient received a therapeutic dose of iodine-131. IFNβ-1b therapy was discontinued. The coexistence of thyroid cancers in MS patients could be explained by immune-mediated inflammation. Although EBV is not the only agent responsible for the development of MS or thyroid cancers, it could be considered a contributory factor in our case. Further research on EBV involvement in the occurrence of simultaneous immune pathologies in various organs is needed to confirm these data.