Paraneoplastic Cerebellar Degeneration Associated with Breast Cancer—A Case Report—

Abstract

A 53-year-old woman presented to the emergency department with progressive difficulty moving her lower limbs, which significantly impacted her daily life. Brain magnetic resonance imaging showed no abnormalities, but her symptoms persisted. Due to dyspraxia, dysarthria, and horizontal nystagmus, she was admitted for further evaluation and referred to the neurology department. On the same day, a computed tomography scan revealed a 2 cm mass in the left breast and an enlarged lymph node in the left axilla. Suspected of having breast cancer, she was referred to our department for evaluation and treatment. Aspiration biopsy of the breast mass confirmed invasive ductal carcinoma, and cytology of the axillary lymph nodes revealed metastatic carcinoma. Additionally, blood tests showed positivity for the anti-Yo antibody. Based on these findings, a diagnosis of breast cancer with paraneoplastic cerebellar degeneration was made. Left mastectomy and axillary lymph node dissection (level I/II) were then performed. The pathological stage was determined to be pT2N2M0 Stage IIIA ER (weakly positive), PgR (-), HER2 (3+), and Ki-60 60-70%. Following surgery, the patient received pulse steroid therapy, anti-HER2 therapy, intravenous immunoglobulin, and cyclophosphamide pulse therapy. This treatment regimen led to gradual improvement in her ataxic symptoms and dysarthria.