Background
Esthesioneuroblastoma (ENB), also known as olfactory neuroblastoma, is a rare neoplasm originating from olfactory neuroepithelium. Approximately 1,000 cases have been identified since Berger and Luc described the first case in 1924. [1] Due to the rare and complex nature of ENB, multiple opinions exist regarding the etiology, optimal staging system, and treatment modalities. These tumors often display varying biologic activity ranging from indolent growth, with patient survival exceeding 20 years, to a highly aggressive neoplasm capable of rapid widespread metastasis, with survival limited to a few months.
Images of esthesioneuroblastomas are shown below.
Esthesioneuroblastoma. Coronal CT scan of the orbits and sinuses shows a large, enhancing, and expansile mass occupying the ethmoid air cells that is invading the cribriform plate and breaking through to the left anterior cranial fossa. Image courtesy of Michael Lev, MD.
Esthesioneuroblastoma. A 39-year-old man presented with 1 month of decreased vision, left facial numbness, and swelling. Physical examination demonstrated left-sided exophthalmos and blindness. He had also lost his sense of smell. Contrast-enhanced T1-weighted MRI demonstrated a large lesion that originated in the paranasal sinuses and extended through the cribriform plate into the anterior cranial fossa. He underwent a bifrontal craniotomy for resection of this tumor.
The prognosis depends on the magnitude of the disease on initial diagnosis. It should be noted that precise histologic diagnosis is difficult because ENBs are often confused with other small round cell neoplasms of the nasal cavity. Despite the difficulties associated with the treatment of ENB, evolving treatment modalities, including surgery, radiation, and adjuvant chemotherapy, have contributed to the better management and increased survival of ENB patients. This article provides an updated summary of ENB, including ongoing research, current thought on pathophysiology, staging, and an update on new surgical techniques used to treat these tumors. [2]
Pathophysiology
Esthesioneuroblastomas (ENBs) are undifferentiated tumors of neuroectodermal origin derived from the olfactory epithelium. [3] The tumor cells are mitotically active and are the precursor cells that develop into sustentacular and neuronal cells. Inconsistent histologic presentations initially led to controversy surrounding the exact histologic origin of ENBs, and this ambiguity can confound clinical and prognostic decisions. In essence, ENBs contain variable arrangements of their small cells. Additionally, there exists a variable presence (or absence) of true rosettes and neurofibrillary material.
To date, no certain genetic factor has been identified that can accurately assist in the diagnosis or predict prognosis. This is partially due to the ability to analyze cancer genomes on a whole genome basis. Recently, a tool called array comparative genomic hybridization was applied to the analysis of ENBs. [4] Although many alterations were identified in this study, chromosomal gains in 7q11 and 20q and deletions in 2q, 5q, 6p, 6q, and 18q have been confirmed by at least 2 other studies. Interestingly, 20q is a region that has been implicated in other cancers, including breast, ovarian, and squamous cell carcinoma. Still, further experimentation will be required to determine the role of these genomic regions in ENB.
The demonstration of human achaete-scute homologue (HASH1) gene expression, although still investigational, could become the diagnostic procedure of choice. [5] The HASH1 gene is involved in olfactory neuronal differentiation and is expressed in immature olfactory cells [6] ; therefore, it could be useful in distinguishing ENB from other poorly differentiated small blue cell tumors.
Epidemiology
Frequency
United States
The incidence of esthesioneuroblastoma in the United States follows trends observed worldwide.
International
Based on the reports in the literature, approximately 1,200 cases of esthesioneuroblastoma (ENB) have been identified since 1924. Interestingly, 80% of these have been identified in the last 25 years. However, the current data set cannot distinguish between a rising incidence and better recognition of the disease. ENB has an estimated incidence of 4 cases per 10 million individuals and accounts for approximately 5% of all sinonasal tumors. Similar incidence rates have been obtained through epidemiologic studies performed in Denmark. [7] To our knowledge, no studies suggest a geographic deviation.
Race
Esthesioneuroblastoma (ENB) does not show a predilection toward any individual race. ENB does not show familial prevalence and has been reported in all races and on all continents.
Sex
Esthesioneuroblastoma (ENB) affects males and females with similar frequency.
Age
Esthesioneuroblastoma (ENB) occurs in a wide range of age groups (3-90 y). There exists a bimodal peak of occurrence in the third and sixth decades of life.
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Esthesioneuroblastoma. Coronal CT scan of the orbits and sinuses shows a large, enhancing, and expansile mass occupying the ethmoid air cells that is invading the cribriform plate and breaking through to the left anterior cranial fossa. Image courtesy of Michael Lev, MD.
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Esthesioneuroblastoma. A 39-year-old man presented with 1 month of decreased vision, left facial numbness, and swelling. Physical examination demonstrated left-sided exophthalmos and blindness. He had also lost his sense of smell. Contrast-enhanced T1-weighted MRI demonstrated a large lesion that originated in the paranasal sinuses and extended through the cribriform plate into the anterior cranial fossa. He underwent a bifrontal craniotomy for resection of this tumor.
Tables
| Grade | Lobular Architecture Preservation | Mitotic Index | Nuclear Polymorphism | Fibrillary Matrix | Rosettes | Necrosis |
| I | + | Zero | None | Prominent | HW rosettes | None |
| II | + | Low | Low | Present | HW rosettes | None |
| III | +/- | Moderate | Moderate | Low | FW rosettes | Rare |
| IV | +/- | High | High | Absent | None | Frequent |
