Sinonasal teratocarcinosarcoma ("mixed olfactory neuroblastoma-craniopharyngioma") presenting with syndrome of inappropriate secretion of antidiuretic hormone.

Sinonasal teratocarcinosarcoma (SNTC) is a rare, aggressive, histologically heterogeneous neoplasm of the paranasal sinuses and nasopharnyx of adults that is composed of variably benign or malignant neuroepithelial, epithelial, and mesenchymal elements. Occasional cases show intracranial extension and may be operated on by neurosurgeons and encountered by neuropathologists who may not be familiar with the entity. STNCs have not previously been associated with functional hypersecretory status. We report a 59-year-old male who presented with headache and syndrome of inappropriate secretion of antidiuretic hormone (SIADH) and was subsequently found to have a bulky tumor of the frontal and ethmoid sinuses with focal dural invasion. The tumor was predominantly composed of olfactory neuroblastoma areas (90% of tumor) admixed with unusually well-developed craniopharyngioma-like mature squamous epithelium and ghost cells ( 10% of tumor). Scattered neuroblastoma tumor cells showed strong immunoreactivity with antibodies to arginine vasopressin, supporting ectopic hormone secretion by the tumor. While the coexistence of neuroectodermal and oral ectodermal-like differentiation in SNTCs is characteristic, in our case it was developed to an extreme functional and morphologic degree and was unassociated with other mesenchymal or epithelial elements often found in these complex tumors. SNTCs with limited differentiation have prompted controversy in classification.