A 74-year-old woman was admitted to our centre for a week presenting with a sensation of rotatory vertigo with nausea and vomiting, gait instability, horizontal binocular diplopia and speech disturbances. Her personal history included an allergy to iodinated contrast dye and infiltrating ductal breast carcinoma with positive oestrogen and progesterone receptors and negative nodes three years earlier. She underwent surgical treatment and radiotherapy of the residual breast. She was currently in remission and was being treated with anastrozole. Physical examination revealed slurred speech, nystagmus with a rapid rotatory component in all directions of gaze, paresis of the right fourth cranial nerve, disabling truncal ataxia with inability to walk and dysmetria in all four limbs. Upper cortical functions were preserved. General tests showed: normal haemogram, general biochemistry and haemostasis. The usual tumour markers (CA 125, CA 15-3, CA19-9, alpha-fetoprotein and carcinoembryonic antigen) were normal. A neuroimaging study with computed tomography (CT) and magnetic resonance imaging (MRI) of the brain was performed and was normal. FCD was suspected and anti-Yo antibodies were determined and were positive at high titres in serum and CSF. While the study of occult neoplasia was being performed, treatment with immunoglobulins, cyclophosphamide and methylprednisolone was started without evident clinical improvement. Thoracic-abdominal CT, mammography, breast MRI and bone scintigraphy showed no evidence of tumour pathology. Positron emission tomography (PET) showed two 15 mm nodular lesions located behind the pancreatic head compatible with mesenteric adenopathy of malignant aetiology. No other foci suspicious for malignancy were observed. Laparotomy and biopsy were performed. The anatomopathological study showed the presence of metastases of poorly differentiated adenocarcinoma. The diagnosis of metastasis of breast carcinoma was considered and the Medical Oncology Department started treatment with epirubicin and cyclophosphamide. The clinical evolution of the patient was towards stabilisation without improvement of signs and symptoms, the patient was not able to perform activities of daily living on her own and needed a wheelchair to move around.