CDR2 and breast adenocarcinoma: Purkinje cytoplasmic autoantibody type 1 (PCA-1, also known as anti-Yo) is a biomarker of paraneoplastic neurological autoimmunity, usually manifesting as cerebellar ataxia (paraneoplastic cerebellar degeneration) in women with gynecologic or breast adenocarcinoma (1, 2).