Neuroendocrine lung cancer in a patient with limbic encephalopathy due to anti-Hu antibodies: A rare association not to be missed

Paraneoplastic neurological syndromes (PNSs) are conditions secondary to the production of autoantibodies against antigens expressed by the tumor cells for cross-reaction with the same antigens in normal cells. However, they are not directly related to the effect of primary tumor or its metastasis [ ]. PNSs, which are often associated with lung cancer, usually precede the discovery of the neoplasm and can be reversed by its treatment. Therefore, early diagnosis is crucial for successful therapy [ ]. Among recognized autoantibodies, anti-Hu antibodies (anti-Hu Ab) are usually related (>90% of cases) to small cell lung cancer (SCLC) [ , , ]. More rarely, anti-Hu Ab have been reported in association with other lung tumors, neuroblastoma, sarcoma, prostate cancer, lymphoma, and gynecological tumors [ , ]. The association of anti-Hu Ab and neuroendocrine cancer has been found in a very few cases [ ]. Both benign and malignant neuroendocrine tumors (NETs) can produce traceable metabolic substances, such as chromogranin A or synaptophysin, which can be useful diagnostic and prognostic markers [ ]. Octreotide scintigraphy (Octreo-Scan) can earlier and more precisely recognize NETs, due to its high affinity (o sensitivity) to somatostatin receptors expressed on neuroendocrine cells surface [ ]. The utility of Octro-Scan in detecting endocrine paraneoplastic syndromes in bronchial carcinoid tumors or paraneoplastic syndromes secondary to neuroendocrine tumors (such as gastrinomas or Zollinger-Ellison syndrome) or in gastrointestinal tumors is described in literature, but its use in paraneoplastic neurological syndromes has not been reported.