Paraneoplastic syndromes are a group of rare disorders that include Paraneoplastic cerebellar degeneration (PCD). Paraneoplastic syndromes are thought to result from an abnormal immune response to an underlying (and often undetected) malignant tumor. PCD is a rare, non-metastatic complication of cancer. PCD is typically thought to be caused by antibodies generated against tumor cells. Instead of just attacking the cancer cells, the cancer-fighting antibodies also attack normal cells in the cerebellum. PCD occurs most often in individuals with the following cancers: ovarian cancer, cancer of the uterus, breast cancer, small-cell lung cancer, and Hodgkin lymphoma. Symptoms of PCD may include dizziness, loss of coordination, blurred vision, nystagmus, ataxia, and speech difficulties.