Abstract
Paraneoplastic cerebellar degeneration (PCD) is a rare neurological complication of cancer characterized by rapid development of cerebellar ataxia. We herein present a case of a 67-year-old female patient with PCD caused by breast cancer. The patient presented with progressively worsening cerebellar deficits that had been misdiagnosed for several months prior to the identification of the anti-Yo autoantibodies in the serum. A whole-body positron emission tomography/computed tomography scan revealed a lesion in the lower outer quadrant of the left breast with slightly increased metabolism. On mammography, a lobulated high-density mass was identified in the left breast. The patient underwent left breast lumpectomy and the histological examination confirmed the presence of an invasive ductal carcinoma. After breast surgery, the patient exhibited marked neurological improvement at the 12-month follow-up. Therefore, it is crucial that clinicians include paraneoplastic neurological syndromes in the differential diagnosis of neurological disorders. The detection of characterized onconeural antibodies in the serum or cerebrospinal fluid may provide guidance in the search for an underlying tumor.