Sinonasal papillomas are rare benign epithelial tumors of the Schneiderian mucosa, accounting for 0.5%-4% of primary nasal lesions, classified into three histologic subtypes—exophytic, inverted, and oncocytic.^[1,2] The oncocytic variant, also termed sinonasal oncocytic papilloma (SNOP), is the rarest and least studied. SNOP is characterized histologically by exophytic and endophytic growth, eosinophilic oncocytic cytoplasm, and intraepithelial microcysts, distinguishing it from inverted and exophytic papillomas.^[3,4] It most often arises in the maxillary or ethmoid sinus and affects both sexes equally. Despite being benign, it shows recurrence rates up to 40% and malignant transformation in 4%-17% of cases.^[4,5] We present an unusual case of SNOP localized to the inferior turbinate, underscoring its rarity and the importance of integrating histopathology, endoscopy, and imaging for accurate diagnosis.

A 67-year-old man was referred to our clinic by his neurologist for evaluation and management of a persistent, medication-free headache in the frontal and parietal regions that had lasted for the past year, accompanied by nasal discomfort, increased nasal discharge, and nasal obstruction, predominantly in the right nasal cavity. No pathology was detected in other structures on the remaining otorhinolaryngological examination. The neurologist had previously ordered magnetic resonance imaging (MRI) of the brain and the facial skull, with contrast substance, which revealed a markedly enhancing mass on T1-weighted sequences(Fig. 1). The patient’s medical history was significant for non-Hodgkin lymphoma diagnosed 20 years earlier, for which he underwent splenectomy and chemotherapy. A recurrence occurred 10 years later, managed again with chemotherapy. Since then, he had remained cancer-free. He reported no history of allergies. Nasal endoscopy at our hospital demonstrated a small mass with polypoid degeneration located on the tail of the right inferior turbinate(Fig. 1a). A computed tomography (CT) scan of the facial skull with contrast substance was subsequently performed before biopsy to delineate the mass’s margins and evaluate possible paranasal sinus involvement. The CT scan revealed a well-circumscribed soft-tissue lesion confined to the right inferior turbinate, without evidence of local extension or bone erosion. Based on these findings, the lesion was initially suspected to be benign.

However, given the patient’s prior history of lymphoma relapse, a positron emission tomography scan with a computed tomography (PET-CT) scan was recommended. According to the literature, SNOP may demonstrate intense fluorine-18-fluorodeoxyglucose (FDG) uptake, which can mimic squamous cell carcinoma (SCC) and other malignancies. In this case, the PET-CT scan was negative, showing no FDG-avid lesions. The patient subsequently underwent a biopsy of the mass under local anesthesia with mild sedation. Prior to the biopsy, we prescribed intranasal corticosteroids and antihistamines for one month; however, he experienced no improvement. Histopathological analysis confirmed the diagnosis of SNOP. Specifically, histological examination revealed fragments of a mucosal lesion consistent with an oncocytic sinonasal papilloma. The lesion is benign; however, it carries a risk of local recurrence. Definitive treatment was carried out with endoscopic surgery under general anesthesia. An endoscopic partial turbinectomy of the right maxillary sinus, along with complete resection of the mass, was performed. The postoperative course was uncomplicated. Final histopathology confirmed the presence of SNOP. At one-month follow-up, the patient reported complete resolution of symptoms. Nasal endoscopy at one year demonstrated no evidence of recurrence. The nasal mucosa completely healed, and the remaining inferior nasal turbinate showed no evidence of local recurrence or polypoid degeneration(Fig. 1b). Patient-reported outcomes significantly improved, with a reduction in VAS score from 8 to 0, HIT-6 score from 74 to 38, and SNOT-22 score, which we used to assess nasal breathing, from 59 to 7.

Sinonasal papillomas are classified into inverted, fungiform, and oncocytic subtypes, the latter termed Sinonasal Oncocytic Papilloma (SNOP).^[1,6]SNOP represents only 3%-5% of Schneiderian papillomas and most often arises in the maxillary or ethmoid sinuses, whereas occurrence in the inferior turbinate or sphenoid sinus is exceptionally rare.^[7-9] Recent case reports confirm its rarity and emphasize the diagnostic challenge of differentiating it from inflammatory or neoplastic lesions.^[10,11] Endoscopic surgery remains the treatment of choice; in a 2022 series of 69 patients, recurrence occurred in 15%-20%, primarily due to incomplete excision.^[12] Although benign, SNOP carries a 4%-17% risk of malignant transformation, most commonly to squamous cell carcinoma.^[13] Histologically, it demonstrates papillary or villous architecture lined by oncocytic epithelium with eosinophilic cytoplasm and intraepithelial microcysts, requiring distinction from oncocytoma and oncocytic carcinoma.^[9] Recent molecular studies indicate that HPV infection is uncommon, while KRAS mutations and mitochondrial dysfunction may underlie oncocytic transformation.^[14] Prognosis is favorable with complete excision, but long-term follow-up is essential due to potential delayed recurrence or carcinoma development.^[7,12]CT and MRI help define tumor extent, while PET-CT usually shows high FDG uptake due to mitochondrial density—though our case uniquely lacked FDG avidity despite histologic confirmation.^[15] The unusual localization to the inferior turbinate, combined with the patient’s history of non-Hodgkin lymphoma, underscores both the rarity and diagnostic complexity of this case.