The impact of multidisciplinary approaches on the outcomes of olfactory neuroblastoma treated with postoperative radiotherapy.

BACKGROUND: We investigated the outcomes of postoperative radiation therapy for olfactory neuroblastoma (ONB) and our cross-departmental collaboration to enhance the effectiveness of cancer treatment. METHODS: We retrospectively evaluated 22 patients with ONB who underwent postoperative radiotherapy after tumor resection. En bloc resection was performed; pathology specimens were prepared in coronal sections; and irradiation fields were determined after discussion with radiation oncologists, head and neck surgeons, and pathologists. RESULTS: The overall survival and local control rates were 95.5% and 100%, respectively, at a median 37-month follow-up. The 3- and 5-year disease-free survival (DFS) rates were 64.4% and 56.3%, respectively. Of the 22 patients, 9 (8 Kadish C and 1 Kadish B) had disease recurrence. Of the nine patients, five had positive margins and two had closed margins; cervical lymph node recurrence occurred in six, and distant metastasis with or without cervical lymph node recurrence occurred in three. DFS analysis of risk factors showed no statistically significant differences, but positive margins were a significant recurrence factor in multivariate analysis. CONCLUSIONS: The local control rate of ONB treated with postoperative radiation therapy was 100%. This may be attributed to cross-departmental cooperation between head and neck surgeons, pathologists, and radiation oncologists, which resulted in accurate matching of CT images for treatment planning with the location of the tumor and positive margins. Longer follow-up periods are required to evaluate the effectiveness of our strategy.

Treatment of unilateral olfactory neuroblastoma: Appropriate extent of surgical resection and potential for olfactory preservation.

Historically, comprehensive surgical resection for olfactory neuroblastoma has included the bilateral olfactory epithelium, cribriform plate, overlying dura, olfactory bulbs and tracts. This results in postoperative anosmia that may significantly impact a patient's quality of life without definitive added benefit in survival. The prevalence of occult intracranial disease is low, especially for Hyams grade I and II tumors. A unilateral approach sparing the contralateral cribriform plate and olfactory system can be considered for select cases of early stage, low-grade tumors when the disease does not cross midline to involve the contralateral olfactory cleft or septal mucosa and when midline dural margins can be cleared with frozen pathology. Approximately half of patients who undergo unilateral resection may have residual olfaction even with adjuvant unilateral radiation. Early data suggest favorable disease-free survival and overall survival for patients who underwent the unilateral approach; however, larger sample studies are needed to confirm comparability to bilateral resections regarding oncologic outcomes.

Peptide Receptor Radionuclide Therapy for Recurrent Olfactory Neuroblastoma After Cranioplasty for Surgical Infection: A Case Report.

BACKGROUND: Peputide receptor radionuclide therapy with 177Lu for midgut neuroendocrine metastasis has been clinically approved as a safe treatment. Unresectable metastases of olfactory neuroblastoma have shorter survival due to insufficient effective systemic treatment. CASE REPORT: Herein, we report a patient treated with peputide receptor radionuclide therapy for unresectable recurrent olfactory neusroblastoma following a rare cranial metastasectomy infection. A 50-year-old female patient with olfactory neuroblastoma of Kadish C was initially treated by skull base surgery plus postoperative radiotherapy following chemotherapy. Recurrent disease with neck and intracranial metastases was treated by four salvage surgeries. Surgical site infection following intracranial metastasectomy was treated with debridement and delayed cranioplasty. Peputide receptor radionuclide therapy was performed for unresectable multiple metastases after cranioplasty. Successful therapy using four cycles of peputide receptor radionuclide had neither grade 3 nor grade 4 adverse events. The patient was followed at an outpatient clinic. CONCLUSION: Further case accrual of peputide receptor radionuclide therapy is required to develop a treatment for unresectable olfactory neuroblastoma.

Stereotactic radiosurgery for distant brain metastases secondary to esthesioneuroblastoma: a single-institution series.

OBJECTIVE: Esthesioneuroblastoma (ENB), also known as olfactory neuroblastoma, is a rare, malignant tumor of neuroectodermal origin that arises from the olfactory neuroepithelium. In this study the authors present the first series in the literature on distant brain metastases (BMs) secondary to ENB that were treated with stereotactic radiosurgery (SRS), to evaluate the safety and effectiveness of SRS for this indication. METHODS: A retrospective analysis of clinical and radiological outcomes of patients with ENB who underwent CyberKnife (CK) SRS at a single center was conducted. The clinical and radiological outcomes of patients, including progression-free survival, overall survival, and local tumor control (LTC) were reported. RESULTS: Between 2003 and 2022, 32 distant BMs in 8 patients were treated with CK SRS at Stanford University. The median patient age at BM diagnosis was 62 years (range 47-75 years). Among 32 lesions, 2 (6%) had previously been treated with surgery, whereas for all other lesions (30 [94%]), CK SRS was used as their primary treatment modality. The median target volume was 1.5 cm3 (range 0.09-21.54 cm3). CK SRS was delivered by a median marginal dose of 23 Gy (range 15-30 Gy) and a median of 3 fractions (range 1-5 fractions) to a median isodose line of 77% (range 70%-88%). The median biologically effective dose was 48 Gy (range 21-99.9 Gy) and the median follow-up was 30 months (range 3-95 months). The LTC at 1-, 2-, and 3-year follow-up was 86%, 65%, and 50%, respectively. The median progression-free survival and overall survival were 29 months (range 11-79 months) and 51 months (range 15-79 months), respectively. None of the patients presented adverse radiation effects. CONCLUSIONS: In the authors' experience, SRS provided excellent LTC without any adverse radiation effects for BMs secondary to ENB.

Operative Technique and Complication Management in a Case of Giant Esthesioneuroblastoma Resected by a Combined Transcranial and Endonasal Endoscopic Approach: Technical Case Report.

BACKGROUND AND IMPORTANCE: Esthesioneuroblastoma (ENB) is a rare anterior skull base tumor derived from olfactory epithelium. There are very few operative videos in the literature demonstrating the surgical resection techniques for giant ENB because of their rarity and complexity. In this technical report, we demonstrate the microsurgical resection of a very large and complex high-grade ENB, initially deemed unresectable, through a bifrontal craniotomy and extended subfrontal approach combined with an endonasal endoscopic approach. CLINICAL PRESENTATION: A 34-year-old woman presented with headaches, nasal congestion, and bloody nasal drainage. MRI showed a large nasal cavity mass with extension into the anterior cranial fossa and bifrontal lobes. There was significant bifrontal edema causing headaches and abutting the optic nerves. Initial management with surgical resection was offered to the patient for local tumor control and to preserve her vision. A combined bifrontal craniotomy and endonasal transsphenoidal approach was used for resecting this giant tumor. After achieving gross total resection, we reconstructed the anterior skull base in layers. She developed several postoperative complications which were appropriately managed. CONCLUSION: We demonstrate the surgical resection of a giant ENB through a combined transcranial and endonasal endoscopic approach. We discuss the several postoperative complications in this complex case and the lessons learned.

Long-term survival outcomes and recurrence patterns of olfactory neuroblastoma: A 13-year experience at a single institution.

OBJECTIVES: Olfactory neuroblastoma (ONB), also known as esthesioneuroblastoma, is a rare malignant neoplasm of the nasal vault and anterior skull base. The results of treatment for ONB are relatively good; however, regional and distant metastases can develop several years after definitive treatment. This study aimed to validate the treatment modality of ONB for oncological outcomes, especially for regional recurrence. METHODS: We retrospectively reviewed the medical records of 22 patients diagnosed with ONB at Kyoto University Hospital between 2009 and 2020. Descriptive statistics were calculated, and Kaplan-Meier curves were used. RESULTS: The median follow-up time was 58.2 months. One (4.5%) patient was clinically node positive, (cN+) and the remaining 21 (95.5%) were clinically node negative (cN0) at presentation. Eighteen patients underwent an endoscopic endonasal approach (EEA) for primary resection, and the remaining four patients underwent a combined EEA and transcranial approach. Elective neck dissection was not performed for 21 patients with cN0 ONB, whereas unilateral neck dissection with removal of ipsilateral lateral retropharyngeal node was performed for one patient with cN+ ONB. Postoperative radiotherapy without concurrent chemotherapy was performed only at the primary tumor bed for 21 patients with cN0 ONB, and at the primary tumor bed and bilateral neck for one patient with cN+ ONB. The 5-year overall, disease-specific, and disease-free survival rates were 94.1%, 100%, and 69.6%, respectively. No patients developed local recurrence, but 6 (27.2%) patients experienced recurrence with a median time to recurrence of 36.4 months, including four and two patients who initially developed regional recurrences and bone metastases, respectively. Five (22.7%) patients had delayed neck recurrence. The salvage rate was only 60.0% in the five patients who had delayed neck recurrence. Regarding the level of delayed neck recurrence, 4 (18.2%) patients had lateral retropharyngeal lymph node metastases. CONCLUSION: Patients with ONB have excellent survival outcomes after endoscopic surgical resection of the primary lesion with postoperative radiotherapy only to the primary tumor bed. Despite excellent survival, delayed neck recurrence, including the lateral retropharyngeal lymph node, remains high. Because salvage surgery for lateral retropharyngeal lymph node recurrence is sometimes technically difficult, it may be better to extend the field of postoperative radiotherapy from the primary tumor bed only to include bilateral lateral retropharyngeal lymph node regions in patients with clinically N0 ONB. Further prospective studies with a large number of patients are needed to determine the extent of postoperative radiotherapy.

Olfactory neuroblastoma limited to sphenoid sinus.

Olfactory neuroblastoma (ONB) is a rare tumour of the skull base, typically originating from the nasal cavity and around the cribriform plate. We present the rare case of ONB originating from and limited to the sphenoid sinus in a 42-year old lady. Pre-operatively the lesion was thought to be a sinonasal polyp and underwent functional endoscopic sinus surgery (FESS) and total excision of the polypoid lesion. Review of histology unexpectedly revealed ONB. She underwent further surgery to ensure wide local excision was achieved with negative margins on histology, followed by radiotherapy. This is only the third reported case of ONB limited to the sphenoid sinus and the ninth reported case of primary sphenoid ONB in the literature. We review the literature pertaining with primary sphenoidal ONB here and suggest complete resection is indicated in ectopic ONB, not unlike classical ONB. There may be a role for adjuvant oncological treatments and lifelong follow up in a multidisciplinary approach is recommended.

Hemicraniectomía endonasal por estesioneuroblastoma: informe de un caso / Endonasal hemicraniectomy by esthesioneuroblastoma: report of a case

El estesioneuroblastoma es una neoplasia maligna que se origina del epitelio olfatorio. El tratamiento se establece de acuerdo con su extensión y el grado histológico de atipia y puede incluir cirugía, cirugía más radioterapia o más radioquimioterapia. Se han utilizado diferentes abordajes quirúrgicos que incluyeron incisiones faciales y craneotomía pero, con la mayor experiencia adquirida en cirugía endoscópica de senos paranasales y el trabajo en equipo con el neurocirujano, se han desarrollado técnicas endonasales que posibilitan realizar resecciones oncológicas en pacientes seleccionados, con menos morbilidad, internación breve y sin comprometer el control local de la enfermedad. Describimos el caso clínico de una paciente con un estesioneuroblastoma con invasión intracraneal, que fue tratada con éxito mediante una hemicraniectomía endonasal preservando el bulbo olfatorio contralateral. (AU)

Esthesioneuroblastoma is a malignant neoplasm that originates from the olfactory epithelium. Treatment is established according to its extension and the histological degree of atypia and may include surgery, surgery more radiotherapy or more chemoradiation therapy. Different surgical approaches have been used, including facial incisions and craniotomy, but with the greater experience acquired with endoscopic sinus surgery and teamwork with the neurosurgeon, endonasal techniques have been developed that make it possible to perform oncological resections in selected patients, with less morbidity, brief hospitalization and without compromising local control of the disease. We describe the clinical case of a patient with an esthesioneuroblastoma with intracranial invasion who was successfully treated by endonasal hemicraniectomy preserving the contralateral olfactory bulb. (AU)

Metastatic esthesioneuroblastoma recurrence after 19 years of remission: A systematic review with case illustration.

PURPOSE: Esthesioneuroblastoma (ENB) is a rare malignant neoplasm of the olfactory epithelium with an estimated incidence of 0.4/million. It can directly extend along the cribriform plate in order to metastasize to the central nervous system. However, non-contiguous intracranial involvement without recurrence at the primary site is extremely uncommon. In this report, the authors review the literature and present a case of non-contiguous intracranial metastasis of ENB without recurrence at the primary site. To the best of our knowledge, this case presents the longest disease-free interval reported in the literature. METHODS: A systematic review of literature was conducted in accordance with the PRISMA guidelines. Additionally, the presentation, surgical management, and post-operative outcomes of an 82-year-old female with non-contiguous intracranial metastasis of ENB after 19 years of remission are described. RESULTS: A total of 137 deduplicated works were identified after the search. Of these, 6 papers satisfied our inclusion criteria for our systematic review. Average age at presentation was 50.8 years (range: 26-66) and 52.6% of patients were female. A majority of cases achieved gross-total resection and received adjuvant radiotherapy for initial treatment. The median interval to intracranial metastasis was 6 years from the time of primary tumor presentation. The median overall survival from ENB recurrence with non-contiguous intracranial metastasis was 11.5 months. CONCLUSIONS: ENB is a highly recurrent tumor and harbors the potential to involve the intracranial space even years after remission. Intracranial involvement entails poor overall survival. Lifetime radiographic follow-up should be considered in all patients with ENB.

Nasoethmoidal Schwannoma as a Mimicar of Esthesioneuroblastoma: A Case Report and Literature Review.

Nasoethmoidal schwannomas are rare lesions and their presentation with intracranial extension is even rarer. Here, a patient presenting with rhinorrhea, epistaxis, and proptosis of left eye was diagnosed with giant nasoethmoidal schwannoma extending to frontal lobe and orbit, which was managed with bifrontal craniotomy with endoscopic transnasal gross total excision. This being predominantly a benign lesion has good prognosis if total excision is achieved.

Long-term oncologic outcomes in esthesioneuroblastoma: An institutional experience of 143 patients.

OBJECTIVE: Esthesioneuroblastoma (ENB) is a rare malignant neoplasm arising from the olfactory epithelium of the cribriform plate. The goal of this study was to update our oncologic outcomes for this disease and explore prognostic factors associated with survival. MATERIALS AND METHODS: We performed a retrospective analysis of patients with ENB treated at a single tertiary care institution from January 1, 1960, to January 1, 2020. Univariate and multivariate analysis was performed. Overall survival (OS), progression-free survival (PFS), and distant metastasis-free survival (DMFS) were reported. RESULTS: Among 143 included patients, the 5-year OS was 82.3% and the 5-year PFS was 51.6%; 5-year OS and PFS have improved in the modern era (2005-present). Delayed regional nodal metastasis was the most common site of recurrence in 22% of patients (median, 57 months). On univariate analysis, modified Kadish staging (mKadish) had a negative effect on OS, PFS, and DMFS (p < 0.05). Higher Hyams grade had a negative effect on PFS and DMFS (p < 0.05). Positive margin status had a negative effect on PFS (p < 0.05). Orbital invasion demonstrated worsening OS (hazard ratio, 3.1; p < 0.05). On multivariable analysis, high Hyams grade (3 or 4), high mKadish stage (C+D), and increasing age were independent negative prognostic factors for OS (p < 0.05). High Hyams grade (3+4), high mKadish stage (C+D), age, and positive margin status were independent negative prognostic factors for PFS (p < 0.05). High Hyams grade (3+4) was an independent negative prognostic factor for DMFS (p < 0.05). CONCLUSIONS: Patients with low Hyams grade and mKadish stage have favorable 5-year OS, PFS, and DMFS.

How I do it: endonasal transcribriform approach for resection of esthesioneuroblastoma.

BACKGROUND: Olfactory neuroblastoma, also known as esthesioneuroblastoma, accounts for only 3-6% of sinonasal malignancies but confers a 40% 5-year overall survival. METHOD: The authors describe techniques for the endonasal, minimally invasive resection of an esthesioneuroblastoma in a 69-year-old man who presented with headaches and anosmia and describe surgical nuances and their effect on adjuvant therapy planning. CONCLUSION: This approach, along with microsurgical techniques, helped increase tumor visualization, improved marginal resection, and reduced surgical risk, which may improve patient outcomes. Multilayered reconstruction with a synthetic dural substitute and creation of a nasoseptal flap were performed to reduce postoperative cerebrospinal fluid leak.

Survival impact of postoperative radiotherapy in patients with olfactory neuroblastoma: 513 cases from the SEER database.

PUPOSE: To evaluate the impact of postoperative radiotherapy (PORT) on survival in olfactory neuroblastoma (ONB) patients with different tumor staging. MATERIAL AND METHODS: Patients with ONB were selected in the Surveillance, Epidemiology and End Results (SEER) database from 2004-2016. Survival analyses were performed using Kaplan-Meier (K-M) method, Cox regression analysis, and competing risk model. RESULTS: A total of 513 patients were included in the study. Univariate and multivariate analysis results demonstrated that PORT was not an independent prognostic factor for overall survival (OS) of modified Kadish stage A and B patients (P=0.699 and P=0.248, respectively). Kadish stage C and D patients who underwent PORT had significantly better OS than those who did not undergo PORT (P=0.03 and P<0.0001). K-M curves revealed that the 5- and 10-year OS rates of patients who underwent PORT vs. non-PORT were 85.3% vs. 70.4% and 68.2% vs. 56.8% in stage C patients, respectively. For stage D patients, the 5-year OS rates were 70.7% and 42.6%, and 10-year OS rates were 53.4% and 29.5% in the PORT and non-PORT groups, respectively. The competitive risk model revealed that the 5-year cancer-specific cumulative mortality incidence decreased by 26.6% while the 10-year mortality incidence decreased by 41.4% in Kadish stage C patients who were treated using PORT; meanwhile, for Kadish stage D patients who were treated with PORT, the 5- and 10-year mortality incidences were reduced by 35.3% and 42.6%, respectively. Furthermore, we found that chemotherapy was not related to the prognosis of ONB patients (all P>0.05). CONCLUSION: Our results indicate that PORT improved survival outcomes of modified Kadish stage C and D ONB patients. However, PORT may not affect survival for modified Kadish stage A and B individuals. Chemotherapy was not recommended for ONB; therefore, further studies are warranted to determine its therapeutic significance.

Absence of Survival Improvement for Patients with Esthesioneuroblastoma Over the Past 2 Decades: A Population-Based Study.

OBJECTIVE: Esthesioneuroblastoma (ENB) is a rare malignancy of the sinonasal tract and its infrequency has confounded efforts at clearly describing the survival trends associated with this neoplasm over the years. In this study, we reviewed survival trends in ENB and investigated the impact of treatment extent and modality on patient outcomes. METHODS: We accessed the Surveillance, Epidemiology, and End Result (SEER) program to identify ENB cases from 1998 to 2016. A χ2 test was used to compare the categorical covariates and a t test or Mann-Whitney U test was utilized for continuous variables. The impact of prognostic factors on survival was computed using a Kaplan-Meier analysis and multivariate Cox proportional hazards model. We divided ENB patients into 4 periods including 1998-2002, 2003-2007, 2008-2012, and 2013-2016, and investigated survival trends using the Kaplan-Meier curve and log-rank test. RESULTS: ENB patients who underwent biopsy alone were associated with older age, larger tumor diameter, increased rates of tumor extension, nodal/distant metastases, and advanced stages as compared with patients undergoing tumor resection. Our results also demonstrated that surgical resection and adjuvant radiotherapy could confer survival advantages, whereas chemotherapy was associated with reduced survival in patients with ENB. Over the past 2 decades, surprisingly, there has been no change in survival rates for patient with ENB (P = 0.793). CONCLUSIONS: Despite advanced diagnostic studies and modernized treatment approaches, ENB survival has remained unchanged over the years, calling for improved efforts to develop appropriate individualized interventions for this rare tumor entity. Our results also confirmed that surgery and adjuvant radiotherapy is associated with improved patient survival whereas the use of chemotherapy should be considered carefully.

Psychophysical assessments of olfaction after endoscopic unilateral resection with post-operative radiotherapy in olfactory neuroblastomas.

Endoscopic resection with post-operative radiotherapy has been included in the standard therapeutic options for olfactory neuroblastomas (ONBs). Recent publications have indicated the feasibility of olfactory preservation after endoscopic unilateral resection of ONBs. This study validated residual olfaction using the psychophysical assessment, T & T olfactometer, in patients who underwent endoscopic unilateral resection with post-operative radiotherapy. A single-institutional retrospective review was performed to identify patients who underwent endoscopic unilateral resection of ONBs with olfaction monitoring using T & T olfactometer between 2009 and 2020. T & T olfactometry was performed before surgery, after surgery, before radiotherapy, and after completion of radiotherapy. Four patients (one female and three males) were identified. The mean observation period was 41.9 months, and all patients showed no evidence of disease. Three patients exhibited residual olfactory function with two patients having normal or pre-operative level olfaction, although T & T olfactometer results showed a temporary increase in recognition thresholds after surgery. As consequence, endoscopic unilateral resection can achieve satisfactory olfactory preservation in patients with early-stage ONBs.

Ectopic Primary Olfactory Neuroblastoma: Case Series and Literature Review.

OBJECTIVE: Olfactory neuroblastoma (ONB) is a rare malignant tumor arising in the upper nasal cleft. Rarely, ONB may originate in ectopic sites and the impact of this on prognosis and treatment strategies continues to be debated. METHODS: A retrospective analysis was undertaken of patients with ectopic ONB treated between 2000 and 2020 in a tertiary-care referral center for skull base tumors. Three patients were included in this analysis: a 37-year-old woman with ONB arising from the bulla ethmoidalis; a 28-year-old man with inappropriate secretion of antidiuretic hormone caused by a maxillary sinus ONB; and a 41-year-old man with lacrimal sac ONB. Preoperative workup, surgical approach, adjuvant treatments and postoperative surveillance were analyzed. Relevant literature published between 2000 and January 2021 was fully reviewed to investigate oncologic outcomes and delineate the standard of care for such rare tumors. RESULTS: All patients were treated via endoscopic endonasal resection with radical intent, followed by adjuvant treatments when required. No recurrences of disease were observed after a mean follow-up time of 32 months (range, 12-60 months). Data emerging from the literature suggest that a multidisciplinary treatment approach, including free-margins surgical resection followed by adjuvant radiotherapy or radiochemotherapy, is recommended. Olfactory bulb and dura preservation should be attempted whenever feasible. CONCLUSIONS: Endoscopic endonasal surgery should be preferred, when possible, to achieve complete excision to minimize patients' morbidity. The ectopic site of origin affects prognosis and should be considered when selecting the appropriate multimodal treatment strategy.

Radiotherapy of sinonasal cancers.

We present the update of the recommendations of the French society of radiotherapy and oncology on the indications and the technical methods of carrying out radiotherapy of sinonasal cancers. Sinonasal cancers (nasal fossae and sinus) account for 3 to 5% of all cancers of the head and neck. They include carcinomas, mucosal melanomas, sarcomas and lymphomas. The management of sinonasal cancers is multidisciplinary but less standardized than that of squamous cell carcinomas of the upper aerodigestive tract. As such, patients with sinonasal tumors can benefit from the expertise of the French expertise network for rare ENT cancers (Refcor). Knowledge of sinonasal tumour characteristics (histology, grade, risk of lymph node involvement, molecular characterization, type of surgery) is critical to the determination of target volumes. An update of multidisciplinary indications and recommendations for radiotherapy in terms of techniques, target volumes and radiotherapy fractionation of the French society of radiotherapy and oncology (SFRO) was reported in this manuscript.

Esthesioneuroblastoma Presenting With Orbital Hypertelorism and Foster-Kennedy Syndrome.

ABSTRACT: Esthesioneuroblastoma is a rare neoplasm originating from the olfactory neuroepithelium at the cribriform plate. The superior nasal cavity is primarily affected. Morbidity and mortality are related to locally destructive growth as well as metastatic potential. Orbital involvement is associated with decreased survival. The authors describe a case of advanced esthesioneuroblastoma with bilateral orbital involvement, presenting with a rare constellation of orbital hypertelorism and Foster-Kennedy Syndrome.

Excisional biopsy and radiotherapy for management of an olfactory neuroblastoma in an axolotl (Ambystoma mexicanum).

CASE DESCRIPTION: A 4-year-old sexually intact male leucistic axolotl (Ambystoma mexicanum) was presented with a 2-week history of dysrexia and difficulty swallowing. CLINICAL FINDINGS: Physical examination revealed a 1-cm-diameter intraoral mass on the rostral aspect of the palate and swelling of the left nasal fossa. Local invasion into the left nasal fossa was suspected during oral examination. The lesion was marginally excised, and an incompletely excised olfactory neuroblastoma was diagnosed histologically. Five weeks later, physical examination revealed persistent erythema, delayed healing of the rostral portion of the palate, and a mild facial deformity associated with a white mass in the nasal cavity. TREATMENT AND OUTCOME: 6 weeks after excision, adjuvant electron (6-MeV) beam radiotherapy was initiated for treatment of the incompletely excised olfactory neuroblastoma and likely presence of a recurrent mass. The protocol consisted of 4 weekly fractions of 8 Gy each (total, 32 Gy) with the axolotl under anesthesia. No acute adverse radiation effects were noted following radiotherapy. The oral erythema resolved after the third session. No recurrence was observed 2 months after treatment, and the owners reported no abnormal signs at home. The axolotl died 3.5 months after radiotherapy was completed (8 months after marginal excision of the tumor) secondary to an environmental management failure. Postmortem histologic evaluation showed no evidence of neoplasia. CLINICAL RELEVANCE: In axolotls, olfactory neuroblastoma should be considered in the differential diagnosis of intraoral palatal masses. This report describes the first application of radiotherapy for treatment of an olfactory neuroblastoma in an axolotl.