ABSTRACT
The authors report a case of sinonasal teratocarcinosarcoma in a 37-year-old man, which was located in the anterior skull base and extended to the right nasal cavity and paranasal sinuses. The tumor was surgically resected twice, but it could not be removed completely. Microscopically, it was mainly composed of primitive cell nests within a moderately cellular stroma. The components of squamous cell epithelia with focal teratoid appearance and adenocarcinomatous differentiation were observed. There were many rhabdomyoblasts scattered in the nests and stroma. Ultrastructurally, the primitive cells had many neural processes with parallel microtubules, resembling olfactory neuroblastoma. Rhabdomyoblasts showed various degrees of skeletal muscle differentiation. Some of the stromal spindle cells had actin filaments with dense patches and dense core granules. Immunohistochemically, the primitive cells were positive for epithelial markers, neuron-specific enolase, synaptophysin, and myogenic regulatory proteins. The rhabdomyoblasts showed immunoreactivity for myoid markers, cytokeratin, epithelial membrane antigen, and synaptophysin. Most of the stromal spindle cells were positive for smooth muscle actin, neuron-specific enolase and synaptophysin. The immunohistochemical and ultrastructural findings suggest that primitive cells had the most primitive phenotype of placodes, and support the possibility that sinonasal teratocarcinosarcoma is essentially a neuroectodermal tumor with divergent differentiation.