Seromucinous Hamartoma of the Nasal Cavity: A Rare Entity Presenting a Diagnostic Challenge in Preoperative Biopsy

Background/Objectives: Seromucinous hamartoma (SH) is an extremely rare benign glandular lesion arising in the nasal cavity and paranasal sinuses, characterized by proliferation of serous and mucinous glands. Preoperative diagnosis by biopsy is extremely uncommon, making it a diagnostic challenge. We report a case of SH and discuss its diagnostic difficulties and management. Case Presentation: A 52-year-old man presented with right-sided nasal obstruction. A lobulated mass in the posterior right nasal cavity was incidentally detected during transnasal endoscopy. The lesion persisted for one year without reduction. CT, MRI, and biopsy failed to provide a definitive diagnosis. The patient was referred to our department, and endoscopic surgery under general anesthesia was performed. The tumor was removed en bloc. Histopathological examination revealed glandular proliferation of mixed serous and mucinous glands within the subepithelial stroma, consistent with SH. Discussion: Preoperative diagnosis is difficult due to insufficient biopsy depth and limited recognition of this rare entity. Since the surface epithelium shows no atypia, identification of subepithelial glandular proliferation is essential. Larger and deeper biopsy specimens and communication with pathologists may improve diagnostic yield. Surgical excision is the treatment of choice. As SH often arises in the posterior nasal cavity and is highly vascular, en bloc resection under general anesthesia is recommended. Conclusions: Recognition of SH is important to improve diagnostic accuracy. Appropriate biopsy strategy and surgical planning based on tumor location are essential.