GRN and lymphoma: PGRN in Serum and CSF was not elevated in patients with AE due to paraneoplastic origin although PGRN is also known as a tumor marker for certain tumors such as Lymphomas (44) The missing correlation between the serum-PGRN and CSF-PGRN is pointing at a cerebral origin of the CSF-PGRN as already seen in other diseases (26, 27).