Ectopic primary olfactory neuroblastoma: Clinical management of an extremely rare entity

Olfactory neuroblastoma (ONB) is a rare malignant neoplasm of neuroectodermal origin. Within an already very rare neoplasm, an even rarer and lesser-known entity is ectopic ONB. A 57-year-old female patient was evaluated for a smooth ethmoidal mass. A contrast-enhanced MRI identified a lesion with epicenter in the osteo-meatal complex without cribriform plate and olfactory recesses involvement. Endoscopic guided biopsy showed ONB Hyams II. An endoscopic trans-nasal resection was performed. The postoperative course was uneventful. A definitive histologic examination confirmed a Hyams grade II, Kadish B ONB, corroborating the ectopic localization. Due to the tumor stage and grade, no adjuvant treatment was performed. The patient was free of disease at one-year postoperative follow-up. Ectopic ONB should be considered in the differential diagnosis of a sinonasal mass. Olfactory bulb and dura resection should be dictated by the clinical or radiological involvement of the cribriform plate. • Olfactory estesioneuroblastoma is a rare malignant neoplasm of the nasal cavity. • Staging includes specific radiological imaging and histological examination. • Carefull exposition is required to exclude skull base involvement.