Breast cancer and paraneoplastic cerebellar degeneration.

Of the remote effects of cancer on the neurologic system, paraneoplastic cerebellar degeneration (PCD), characterized by global cerebellar dysfunction, is second only to paraneoplastic neuropathies in frequency. Recent evidence, including the finding of anti-Purkinje cell (now termed anti-Yo) antibodies directed against specific protein antigens shared by Purkinje's and tumor cells, supports an autoimmune etiology for this disorder. Increasingly, a link between breast cancer and PCD is being recognized. The authors report a case, as well as a comprehensive overview, of 62 women with breast cancer and PCD, identified through a Medline (National Library of Medicine, Washington, DC) computer search (1966 to 1991) and comprehensive reference follow-up of the medical literature. The current understanding of the pathophysiology of PCD, with particular emphasis upon those features both salient and unique to breast cancer, is discussed. Whereas PCD will affect only a small number of patients with breast cancer, recognition of this syndrome is important. Anti-Purkinje cell (anti-Yo) antibody titers are now commercially available through several reference laboratories, and a serum anti-Purkinje cell antibody titer will assist in establishing the diagnosis. Presence of consistent symptoms and elevated titers of anti-Yo antibodies should prompt a search for an otherwise occult, and potentially treatable, malignancy. Only therapy initiated early in the patient's course appears to be of benefit. Finally, investigations into the pathogenesis of this syndrome may shed further light upon other diseases presumed secondary to autoimmune dysfunction.