Syndrome of inappropriate antidiuretic hormone secretion in a case of olfactory neuroblastoma without anti-diuretic hormone immunoreactivity: A case report and review of the literature.

Olfactory neuroblastoma (ONB) is a relatively rare nasal or paranasal malignant tumor. This tumor is rarely accompanied by paraneoplastic syndromes such as syndrome of inappropriate antidiuretic hormone secretion (SIADH). Here, we report a 31-year-old female with histologically confirmed ONB who had been diagnosed with SIADH three years prior. She was treated with surgery followed by concurrent chemoradiotherapy. SIADH resolved immediately after surgical tumor resection. Immunohistochemically, both biopsy and resected specimens from the nasal cavity had been negative for ADH. Although extremely rare, ONB may be associated with SIADH, and the possibility of this cancer should be taken into account during the follow-up of idiopathic SIADH.