Olfactory neuroblastoma (ONB) is a rare, malignant tumor of neural crest cell origin that arises from the olfactory mucosa in the superior one-third of the nasal septum, cribiform plate, and superior turbinates. ONB has been referred to by many other names in the literature to include esthesioneuroblastoma, esthesioneuroepithelioma, and esthesioneurocytoma. ONB is a slow-growing, highly-vascular tumor, which leads to the development of progressive symptoms over the course of months to years. Therefore, early diagnosis is uncommon. Symptoms associated with ONB most commonly include unilateral nasal obstruction, anosmia, and epistaxis with frontal headache, pain, excessive lacrimation, and ocular disturbances (i.e. diplopia) occuring less frequently. Physical exam may reveal a mucus-covered, pink-red polypoid mass high in the nasal cavity. ONB can occur at any age, however a bimodal peak occurs in the second and sixth decades.

The diagnosis of ONB requires biopsy with histologic examination along with the use of electron microscopy and immunohistochemistry. Radiographic findings are nonspecific for differentiating ONB from other anterior cranial fossa masses, which include squamous cell carcinoma, extramedullary plasmacytoma, meningioma, lymphoma, sinonasal undifferentiated carcinoma, rhabdomyosarcoma, amelanotic melanoma, and Ewing's sarcoma and related PNETs to name a few. CT and MR imaging are essential for accurate staging and preoperative planning. CT demonstrates a homogeneous soft tissue mass with equal or greater density than the surrounding soft tissue, which enhances with IV contrast. Additionally, focal calcifications and cysts at the intracranial margin may also be present. CT is superior to MR in demonstrating bony involvement and destruction especially on coronal views. MR typically demonstrates a nonspecific hypo to isointense mass on unenhanced T1WI and an iso to hyperintense mass on T2WI that enhances with gadolinium administration. MR is superior to CT in the evaluation of ONB because it allows for imaging of the skull base in any plane and allows for the differentiation of tumor from entrapped sinus fluid and orbital fat.

ONBs typically arise unilaterally within the nasal cavity with subsequent invasion of the bilateral adjacent paranasal sinuses, olfactory bulb, orbits, anterior cranial fossa, or brain. Metastases occur to the cervical lymph nodes, liver, bones, and lungs. Two systems for staging ONBs exist, but their prognostic value is debated within the literature. The Kadish Classification has traditionally been used with Stage A disease confined to the nasal cavity, Stage B confined to the nasal cavity and one or more paranasal sinuses, Stage C disease extending beyond the nasal cavity or paranasal sinuses, and Stage D involving the cervical lymph nodes or distant metastasis. The Dulguerov System is a TMN based classification.

There is no true consensus regarding treatment for ONBs. The current treatment of choice involves craniofacial resection of the tumor and the cribiform plate (due to the high incidence of microscopic disease in the olfactory bulb) with postoperative radiation. However, local recurrence and distant metastases are common despite the above treatment. The role of chemotherapy in localized and metastatic disease remains unclear.