Esthesioneuroblastoma Overview
Esthesioneuroblastoma (ENB), also known as Olfactory Neuroblastoma, is an uncommon malignant tumor of the upper nasal cavity and anterior skull base. It is believed to arise from the olfactory neuroepithelium that lines the cribriform plate, superior aspect of the nasal septum, middle turbinate, and superior turbinate. The olfactory neuroepithelium contains specialized receptor cells that mediate the sense of smell.
ENB was initially described by Berger and Luc in 1924, and is now thought to represent a few percent of all malignant nasal tumors. ENB occurs over a broad age range and has a bimodal age distribution in the second and fifth decade, with most patients in their fifties and sixties. It has a propensity to metastasize to neck lymph nodes, and much less commonly to distant areas in the body. There are no known specific causes or risk factors for developing this tumor.
Symptoms of Esthesioneuroblastoma
Most patients with esthesioneuroblastoma present with symptoms of nasal obstruction (inability to breath through the involved nostril), nosebleed or both. These tumors can spread to the lymph nodes and to other areas of the body. The incidence of metastasis (spread to other body areas) is ~50%.
The most frequent symptoms are a unilateral nasal obstruction (70%), followed by epistaxis (46%). These are common in many nasal diseases, including long-term rhinosinusitis or allergic polypoid sinus disease. Many patients undergo sinus surgery, only to have the diagnosis established as an unexpected pathological finding.
Further growth of the tumor can be directed laterally within the orbit and results in proptosis, extraocular movement paralysis, and blindness, or, it superiorly produces intracranial complications. Facial and oral symptoms are rare.
Diagnosing Esthesioneuroblastoma
A thorough history and a comprehensive head and neck examination are performed initially. Particular attention should be dedicated to the neck examination considering a significant percentage of patients (5-20%) have neck metastases at presentation. Nasal endoscopy is helpful for evaluating tumor location, characteristics and extent, as well as for obtaining a biopsy.
Computed Tomography (CT) and Magnetic Resonance (MR) imaging are often complementary in characterizing the tumor and extension into surrounding structures, especially the orbit and the brain. High-resolution CT remains the initial study of choice. It provides superior bony definition and allows evaluation of the integrity of bony structures surrounding the tumor, such as the orbit, skull base, septum, and palate. However, all patients with the confirmed or suspected diagnosis of ENB should have both CT and MR imaging with exceptions only applying to very small and localized tumors. The main value of MRI lies in its ability to define the extent of the lesion and the involvement of surrounding structures, especially the orbit, skull base, dura, and brain parenchyma. It also helps differentiate between tumor and adjacent inflammatory changes. This information is critical for proper preoperative surgical planning.
Due to the relatively high rate of neck involvement at presentation, a CT neck with intravenous contrast is routinely obtained to evaluate for occult metastasis. Metastatic workup also includes chest and abdomen CT, as well as liver function tests. Alternatively a Positron Emission Tomography (PET) scan could be obtained to evaluate for regional and distant metastases.
