RESUMO
OBJECTIVES: Sinonasal hamartomas are benign neoplasms composed of disorganized mature tissue elements. Epithelial variants include respiratory epithelial adenomatoid hamartoma (REAH) and seromucinous hamartoma (SMH). Malignant transformation of REAH is rarely reported; however, the malignant transformation of SMH to adenocarcinoma has not been described. We report the first case of a transformation from SMH to adenocarcinoma. METHODS: The medical records of a patient presenting with sinonasal SMH with malignant transformation to adenocarcinoma were reviewed. The NCBI database was queried for the literature regarding SMH and malignant transformation of sinonasal hamartomas. RESULTS: A 39-year-old man presented with a left nasal mass, nasal obstruction, and epistaxis. Computed tomography and magnetic resonance imaging demonstrated a nonaggressive and heterogeneous left nasal mass with involvement of the middle turbinate and posterior ethmoid sinuses. He underwent endoscopic sinus surgery with complete excision of the mass. Pathology revealed SMH with focal areas of transition to low-grade adenocarcinoma characterized by stromal invasion but no bony, perineural, or lymphovascular invasion. Adjuvant treatment was not recommended. Literature review revealed no reported cases of malignant transformation of SMH. CONCLUSION: We report the first case of malignant transformation of SMH. Patients with SMH must be counseled that there is an extremely rare and potentially unrecognized risk of malignancy that may influence treatment and postoperative monitoring.