Paraneoplastic neurological syndromes (PNS) caused by occult breast cancer and metastatic carcinoma of the lymph node.

Paraneoplastic neurological syndromes (PNS) are immune-mediated, subacute, and progressive syndromes caused by remote effects of malignant tumours rather than the direct infiltration of tumours. The most common maladies related to PNS are small cell lung cancer, breast and ovarian cancer, and Hodgkin's lymphoma. Diagnoses of PNS frequently precede tumour diagnoses because the primary tumour is often occult. It is difficult for clinicians to recognise PNS, because there are various neurological symptoms and signs in the patient but few abnormal results of the examinations. The examination of paraneoplastic panels (cerebrospinal fluid (CSF) and serum) is useful in the diagnosis of PNS, but the false negatives should be considered. Due to the severe neurological morbidity and mortality caused by PNS, early diagnoses are important to allow for time to treat the underlying tumour and to obtain functional improvement. It is worth noting that regular re-examination and follow-up are crucial for reducing the rates of misdiagnosis and missed diagnosis of PNS.