(A1125) Inverted Papilloma with Focal Respiratory Epithelial Adenomatoid Hamartoma: A Case Report of Interesting Histopathologic Findings

Introduction: Inverted papilloma (IP) is a rare, benign epithelial tumor that arises in the nasal cavity and paranasal sinuses, characterized by its aggressive local behavior and potential for recurrence and malignant transformation. Respiratory epithelial adenomatoid hamartomas (REAHs) are benign sinonasal glandular proliferations, lined by ciliated respiratory epithelium. This report aims to present a rare simultaneous occurrence of IP and RHEA, offering unique diagnostic and clinical insights.

Methods: A 52-year-old male presented to a tertiary rhinology clinic with complaints of persistent nasal obstruction, mouth breathing, and pressure over the left maxillary sinus for the past 5 years. Endoscopic examination of the left nasal cavity revealed a grade 3 middle meatus polyp with fingerlike projections extending from the left maxillary antrostomy, along with a left-sided septal spur. The differential diagnosis included antrochoanal polyp, IP, and malignancy. The patient underwent septoplasty and left endoscopic medial maxillectomy for tumor removal.

Results: Preoperative CT scan findings indicated chronic left maxillary sinusitis with moderate mucosal thickening and no classic hyperostosis typically associated with IP, which aligned with intraoperative observations showing no evidence of hyperostotic bone. Histopathological analysis of the excised lesion revealed fragments of IP with background of focal REAH. Post-operative visits showed no evidence of disease recurrence, and wound healing was managed with saline irrigation and as needed debridement.

Conclusions: To our knowledge, this is the first reported case of IP and REAH appearing together in a single paranasal sinus. REAH and IP have similar histologic features, therefore the coexistence found in this case report highlights the importance of careful pathologic review to prevent misdiagnosis, as IP requires aggressive treatment and surveillance, while REAH needs simple excision with rare recurrence. This case underscores the need for careful detection and differentiation of sinonasal pathologies to guide appropriate management.