Introduction
Esthesioneuroblastoma (olfactory neuroblastoma) is an uncommon malignancy of the nasal cavity. Esthesioneuroblastoma represents 3% to 6% of sinonasal malignancies and has an estimated incidence of 0.4 cases per 1 million people. This tumor has been reported across a wide age range (2 to 94 years) and has no sex predilection. Some case series document a bimodal age peak in the second and sixth decades ; however, others indicate a unimodal peak in the fifth to sixth decades. No environmental, geographic, or lifestyle risk factors have been clearly associated with an increased risk of esthesioneuroblastoma.
Esthesioneuroblastoma is of neural crest origin and arises from the basal stem cells of the olfactory neuroepithelium ( Fig. 45.1 ). The tumor is phenotypically intermediate between a pure neural (e.g., neuroblastoma) and a neuroendocrine epithelial neoplasm (e.g., carcinoid, small cell carcinoma), and there are case reports of the tumor secreting vasopressin.
The most common presenting symptoms are unilateral nasal obstruction and epistaxis; however, less common presenting symptoms include headache, facial pain, rhinorrhea, anosmia, diplopia, decreased visual acuity, proptosis, epiphora, and the syndrome of inappropriate antidiuretic hormone secretion. The tumor is often highly vascular and prone to significant bleeding when biopsied.
On imaging, esthesioneuroblastoma most commonly appears as a nonspecific mass in the superior nasal cavity ( Fig. 45.2 ). However, the classic appearance is of a bilobed mass extending across the cribriform plate ( Fig. 45.3 ). Intratumoral mineralization can be a diagnostic clue to esthesioneuroblastoma; however, this finding is also commonly seen in the setting of inverted papilloma and chondrosarcoma. The presence of cysts at the margins of the intracranial tumor components has been described as diagnostic of esthesioneuroblastoma, but this is rarely seen ( Fig. 45.4 ). The development of marginal cysts associated with esthesioneuroblastoma dural metastases may also be seen ( Fig. 45.5 ).
Several staging systems have been proposed, including the modified Kadish, Hyams, and TNM classifications. Use of these proposed staging systems remains a matter of preference, with none being universally accepted.
Current treatment guidelines recommend complete surgical resection and adjuvant radiotherapy based on improved overall survival with this regimen. Historically the operation of choice has been the craniofacial resection, involving a bifrontal craniotomy in order to remove the cribriform plate, cristi galli, adjacent dura, and olfactory bulbs and tracts en bloc; this remains the standard operation in patients with locally extensive disease. However, endoscopic resection is being more frequently attempted in patients with early-stage tumors confined to the nasal cavity, and some centers are even employing endoscopic techniques for the resection of selected tumors with intracranial extension. The role of systemic chemotherapy for the treatment of esthesioneuroblastoma is not yet well defined.
Temporal Evolution: Overview
Esthesioneuroblastoma arises from the olfactory epithelium of the superior nasal cavity and is most commonly a rapidly growing, aggressive neoplasm ( Fig. 45.6 ). Over time the tumor involves the nasal cavity more extensively and most commonly spreads locally into the paranasal sinuses, orbit, and anterior cranial fossa via the cribriform plate. Regional cervical nodal, pulmonary, and osseous metastases are common.
Less commonly, esthesioneuroblastoma may exhibit a more indolent course ( Fig. 45.7 ), such that relative temporal stability does not exclude esthesioneuroblastoma as a differential consideration for a superior nasal cavity mass.
After treatment, recurrence is most often local. However, the tumor also exhibits a propensity for nodal and distant recurrence irrespective of the initial tumor’s grade, with distant recurrence most commonly occurring in the lungs and bone. Although recurrence is most commonly seen within 2 years of initial treatment, it may not infrequently occur more than 10 years after initial therapy. For this reason, lifelong surveillance is recommended.
Temporal Evolution: in Greater Depth
The olfactory epithelium from which esthesioneuroblastoma arises is usually limited to the cribriform plate, the posterior aspect of the superior turbinate, and the superior nasal septum. Therefore esthesioneuroblastoma almost always develops in these same areas, although rare cases of “ectopic” esthesioneuroblastoma ( Fig. 45.8 ) have been described in the nasopharynx, maxillary sinus, and sella turcica.
Local recurrence ( Fig. 45.9 ) has been reported in up to 60% of patients treated with surgery and radiation, with the majority of recurrences being seen within the first 12 to 24 months. Because of esthesioneuroblastoma’s propensity for late yet often treatable recurrent disease, lifelong imaging surveillance is advised.
Cervical nodal metastases are present in 5% to 10% of patients at presentation and confer a significantly worse prognosis. For this reason, pretreatment imaging of the neck is recommended in patients with esthesioneuroblastoma.
Cervical nodal metastases will ultimately develop in 10% to 44% of patients over the course of their disease. According to one series, level II nodes are most commonly involved (93%); however, involvement of level I (57%), level III (50%), and retropharyngeal (43%) nodes is also commonly seen.
Distant metastases have been reported in up to 7% of patients at the time of initial presentation and occur in up to 25% of patients over the course of the disease. Osseous and pulmonary metastases are most common; however, involvement of the dura ( Fig. 45.10 ), skin, liver, parotid, spinal cord, and brain has also been described.
Although there is no consensus regarding optimal salvage therapy for locally recurrent disease, repeat surgery, repeat radiation, or a combination of both is typically performed.
Posttherapy Evaluation
Craniofacial Resection
Complete surgical resection is the mainstay of esthesioneuroblastoma therapy. Although endoscopic resections are more commonly being attempted at some institutions in early-stage esthesioneuroblastoma, craniofacial resection has historically been the operation of choice and remains the gold standard operation, especially in patients with locally advanced disease. Because of the high risk of local recurrence and the routine practice of lifelong imaging surveillance, it is imperative that the radiologist be familiar with the normal postoperative appearance following craniofacial resection ( Fig. 45.11 ) as well as adept at identifying findings concerning for tumor recurrence.
