A full otolaryngologic and cranial nerve examination should be performed. This should include nasal endoscopy. ENB does not have specific distinguishing features on examination but usually appears as a unilateral polypoid, glistening, soft, red–grey mass with intact mucosa arising in the upper nasal cavity that often bleeds easily on instrumentation. Cervical lymphadenopathy may be palpable in advanced disease. Ectopic tumors within the paranasal sinuses are rare, but have been described in the sphenoid sinus, lateral nasal wall, petrous apex, maxillary sinus, and the nasopharynx [5]. Diagnosis is made via biopsy, which should not be performed until imaging studies are complete. General anesthesia is recommended for biopsy, due to the highly vascular nature of the tumor; a comprehensive endoscopic examination can also be performed at the same time.

All causes of pediatric sinonasal masses must be carefully excluded (Table 17.2).

ENB is histologically very similar to small, round, blue cell tumors. These are important to distinguish, as they respond very differently to different treatment modalities (Fig. 17.1). Tumor cells are “small, round, blue” and mitotically active. The hallmark of well-differentiated ENB is small, round neuroepithelial cells arranged in rosettes (Flexner-Wintersteiner) or pseudorosettes (Homer-Wright) patterns, separated by fibrous elements. Rosettes consist of a central space ringed by columnar cells. Immunohistochemical tests are helpful in differentiating neuroblastomas from other malignant small round cell tumors, however, to date there is no test specific to ENB.[6] (Table 17.3).

Both computed tomography (CT) and magnetic resonance imaging (MRI) are recommended for the workup of ENB. Particular attention needs to be paid to areas such as the lamina papyracea, the fovea ethmoidalis, and the cribriform plate.