A Rare Case of Sinonasal Seromucinous Hamartoma Developing from the Nasal Septum.

A 45-year-old man presented with a history of chronic left nasal congestion. Nasal endoscopy revealed a pedunculated polypoid mass with glandular epithelium surface on the posterior nasal septum. Computed tomography revealed a 25-mm mass-like growth in the left posterior nasal cavity attached to the nasal septum with a stalk. The patient underwent transnasal endoscopic surgery, and the tumor was removed under a block with safety margin. The final pathological diagnosis was sinonasal seromucinous hamartoma (SH). Sinonasal SH is a rare tumor with only 31 reported cases. Transnasal endoscopic surgery is currently the first-line treatment for sinonasal SH. Differential diagnoses of this lesion include inflammatory polyps, respiratory epithelial adenomatoid hamartoma, and adenocarcinoma. Although SH is a benign tumor, its progression to adenocarcinoma has been reported. Therefore, unilateral posterior nasal tumors must be diagnosed precisely.