Olfactory neuroblastoma, also called esthesioneuroblastoma, is a rare, malignant neuroectodermal neoplasm that originates in the superior nasal cavity. While the exact origin of the tumor is unknown, olfactory neuroblastoma is thought to arise from the basal cells of the olfactory epithelium. It accounts for about 3% of all tumors found in the nasal cavity. The disease occurs over a wide age range and most commonly presents in a bimodal distribution in the second and sixth decades of life. There is a slight predilection for males. Risk factors for the disease are unknown.

Common signs and symptoms of olfactory neuroblastoma include unilateral nasal obstruction, nasal discharge, epistaxis, anosmia, frontal headaches, and eustachian tube dysfunction. Patients may also present with vision loss, orbital pain, proptosis, or ophthalmoplegia due to tumor involvement of the orbit. On physical exam, a polypoid mass is often seen in the nasal cavity. As the initial signs and symptoms of olfactory neuroblastoma are similar to those of other common rhinologic diseases, olfactory neuroblastoma may progress significantly before diagnosis. The tumor is locally invasive to the paranasal sinuses, orbit, and the central nervous system. There is a predilection for early metastases to the cervical lymph nodes, most frequently to level II. Tumors metastatic to regional lymph nodes or distant areas portend a worse prognosis than tumors confined to the nasal cavity.

Multiple staging systems exist for olfactory neuroblastoma, but the most commonly used is the modified Kadish staging system:

• Stage A – tumors with sinonasal involvement only
• Stage B – tumors with paranasal sinus extension
• Stage C – tumors with extra-sinus extension
• Stage D – metastatic disease

The Dulguerov system is more descriptive and includes factors that are known to influence survival such as central nervous system involvement, lymph node metastases, and distant metastases.

Olfactory neuroblastoma may also be given a histologic grade using the Hyams grading system. This grading system is divided into grades I through IV (most differentiated to least differentiated) and is based on tumor architecture, presence of mitotic activity, nuclear pleomorphism, neurofibrillary matrix, Homer Wright pseudorosettes, glands, calcification, and necrosis. Some studies have shown worse survival prognosis with Hyams grade III and IV tumors.