Sinonasal Teratocarcinosarcoma, a Rare Tumor Involving Both the Nasal Cavity and the Cranial Cavity.

Sinonasal teratocarcinosarcoma (SNTCS), a very rare tumor, is known to be a heterogeneous with epithelial, mesenchymal, and neuroepithelial components and shows a very aggressive clinical course. Due to the heterogeneity of this tumor, it is often misdiagnosed. No definitive treatment modality has been reported because it is a very rare tumor. A 44-year-old man presented to a rhinologist with headache and nasal obstruction, and an intranasal tumor was found that invaded into the cranial cavity. He underwent combined surgery with a rhinologist and a neurosurgeon following cognitive decline that worsened after a transnasal biopsy. The patient was diagnosed with SNTCS and underwent radiotherapy. However, residual tumor was found during radiotherapy and additional chemotherapy was administered. Follow-up brain MRI revealed no remnant or recurrent lesion. SNTCS is a tumor that has not yet been well researched and should be further investigated for proper treatment.