Ectopic primary olfactoryneuroblastoma : case series and literature review

Objective: Olfactory neuroblastoma (ONB) is a rare malignant tumor arising in the upper nasal cleft. Rarely, ONB may originate in ectopic sites and the impact of this on prognosis and treatment strategies continues to be debated. Methods: Retrospective analysis of patients with ectopic ONB treated between 2000 and 2020 in a tertiary-care referral center for skull base tumors. Three patients were included in this analysis: a 37-year-old female with ONB arising from the bulla ethmoidalis; a 28-year-old male with inappropriate secretion of antidiuretic hormone due to a maxillary sinus ONB; and a 41-year-old male with lacrimal sac ONB. Preoperative workup, surgical approach, adjuvant treatments and post-operative surveillance have been analyzed. Relevant literature published between 2000 and January 2021 was fully reviewed in order to investigate oncological outcomes and delineate the standard of care for such rare tumors. Results: All patients were treated via endoscopic endonasal resection with radical intent, followed by adjuvant treatments when required. No recurrences of disease were observed after a mean follow-up time of 32 months (range, 12-60 months). Data emerging from current literature suggests that a multidisciplinary treatment approach, including free-margins surgical resection followed by adjuvant radiotherapy or radiochemotherapy is recommended. Olfactory bulb and dura preservation should be attempted whenever feasible. Conclusions: Endoscopic endonasal surgery should be preferred, where possible, to achieve complete excision in order to minimize patients' morbidity. The ectopic site of origin impacts on prognosis and should be considered when selecting the appropriate multimodal treatment strategy.