Paraneoplastic cerebellar degeneration: Yo-expressing tumor revealed after a 5-year follow-up with FDG-PET.

We report a patient with anti-Yo associated paraneoplastic cerebellar degeneration (PCD) whose tumor was demonstrated 5 years after developing PCD and had strong expression of Yo (cdr2) antigen. Review of this case along with clinical series and studies of tumor growth rates question the effectiveness of the anti-tumor immune response. These studies and similar cases suggest that the tumor may trigger the anti-Yo immune response at microscopic stages of development. An overwhelming majority of anti-Yo positive patients eventually develop a detectable malignancy, which argues in favor of a poorly effective or non-sustained anti-tumor immune response.