Olfactory Neuroblastoma With Divergent Differentiation: Contemporary Management of Unusual Pathology and Literature Review

Abstract

Olfactory neuroblastoma (ON; Esthesioneuroblastoma) is a malignant tumor that arises from the olfactory neuroepithelium. Very rarely, ON can histologically display a biphenotypic pattern, with only 7 cases reported in the literature to date. We describe a case of this poorly understood entity and review the patient’s histology, pathology, and treatment. An 85-year-old man presented with endoscopy and imaging findings of a sinonasal mass arising from the olfactory cleft. Biopsy and further pathological review established Hyams grade 3 and Kadish stage C tumor. The patient underwent combined endoscopic and open-approach resection due to the involvement of the nasal bone and subsequent adjuvant radiation therapy. Specimen contained Flexner-Wintersteiner rosettes and stained positive for the neuroendocrine marker synaptophysin consistent with ON. A second, epithelial component pattern of goblet cells and mucin was observed suggesting divergent differentiation. We are the first group to report next-generation sequencing of this tumor, which revealed a pathogenic mutation in PIK3CA and a likely pathogenic variant in RUNX1 (AML1). ON with divergent differentiation is very rare, and more robust studies characterizing molecular drivers and pathology may aid in clinical management.

Introduction

Esthesioneuroblastoma, also known as olfactory neuroblastoma (ON) accounts for approximately 3% to 5% of nasal cavity cancers. ¹ These malignant tumors arise from the olfactory neuroepithelium and typically occur in a bimodal age distribution in the second or fourth to sixth decade of life in patients. ² Patients often present with epistaxis, nasal obstruction, or with symptoms of tumor spread to the sinuses, brain, and orbit. The 5-year overall survival rate is up to 80% with multimodal therapy, including surgical resection and adjuvant radiation, with or without chemotherapy. ³ Histologically, ON is evaluated by the Hyams grading system. A score of 1 to 4 is given based on adverse features such as rosette formation, mitotic activity, pleomorphism, necrosis, and disorganized architecture. ⁴ Clinical staging of the tumor is conducted with the Kadish system that classifies lesions into low grade (A, B) or high grade (C, D), with higher grade correlating with greater tumor extension into surrounding structures. ⁵

An exceedingly rare subset of these tumors can display a biphenotypic pattern on histology. They are often described as having divergent or mixed differentiation. Existing literature on this topic includes case presentations and histological findings, with only 7 cases published in the literature to date (Table 1).^6-12 However, there is a lack of consensus on how to classify this tumor type due to the limited number of reported cases. Important clinical variables for this patient group including prognosis have yet to be elucidated. Here, we present a rare case of ON with divergent differentiation, review its histopathology, and discuss the role of next-generation sequencing (NGS) in guiding treatment decisions and future research.

Table 1.

Summary of Literature for Olfactory Neuroblastoma With Divergent Differentiation.

References	Clinical presentation	Imaging results	Histological findings	Immunohistochemistry findings	Final diagnosis
Meyer et al 6	35-Year-old man with right-sided nasal congestion, intermittent epistaxis, headaches, and hyposmia for several months	Mass in the superior right nasal cavity extending and eroding through the cribriform plate and left nasal cavity	- Small round blue cells within the neurofibrillary matrix in small nests, clusters, or individually scattered. - Flexner-Wintersteiner and Homer Wright rosettes noted. - Prominent focal necrosis. - Small, elliptical-to-round epithelioid cells. Variable sizes of nests and ribbons with higher mitotic index and atypical forms. - Overlying mucosa showed several epithelial dysplasia or carcinoma-in- situ.	+Synaptophysin, NSE, CD56. Weakly +chromogranin. Focal islands of cells +S-100. +Pancytokeratin and epithelial membrane antigen.	Olfactory neuroblastoma with divergent differentiation
Gandhoke et al 7	46-Year-old male with epistaxis and nasal obstruction for 4 months	Large heterogeneous mass in left superior nasal cavity with extensions into bilateral maxillary, ethmoidal and sphenoidal sinuses, and anterior cranial fossa	- Lobules, sheets, and nests of primitive cells with high nuclear:cytoplasmic ratio, pleomorphism, round hyperchromatic nuclei with inconspicuous nucleoli and scanty cytoplasm. - Rosette formations noted.	+NSE, synaptophysin, chromogranin, CD56. Peripherally +S100.	Mixed olfactory neuroblastoma-carcinoma (squamous and glandular differentiation) Hyams grade IV
Charles et al 8	31-Year-old man with a history of left nasal mass with extension into anterior cranial fossae 1 year ago presents with left upper eyelid swelling	Heterogeneously enhancing superolateral extraconal orbital mass with hypermetabolic mediastinal lymph nodes with metastatic tumor	- Sheets of poorly differentiated malignant cells interspersed with fibrous septae and zones of necrosis. - Tumor cells with pleomorphic vesicular nuclei with prominent nucleoli. - Occasional Flexner-Wintersteiner rosettes noted.	+CD56, chromogranin, synaptophysin, NSE. +Epithelial markers CAM5.2 and epithelial membrane antigen. +AE1/AE3 for scattered foci of cytokeratin. Ki67 for a high percentage of cells in cell cycle. Spottily +vimentin.	Esthesioneuroblastoma with divergent differentiation (“High-grade olfactory neoplasm with delineation of its varied components”)
Squillaci (2014) 9	81-Year-old female	Mass arising from anterior ethmoid, filling upper portion of the left nasal cavity and sparing sinus cavities	- Atypical monotonous round cells. - Irregular lobulated and nested growth pattern and sparse mitotic figured (3–4 mitoses per 10 HPF). - Focally, ganglioneuroblastic differentiation with large ganglion and spindle cells.	+NSE, CD56, chromogranin, synaptophysin, neurofilament, calretinin. Focal staining +S-100, GFAP, CD99, neurofilament, calretinin, chromogranin, and synaptophysin.	Olfactory neuroblastoma with focal ganglioneuroblastic differentiation
Chang et al (1997) 10	71-Year-old man with right intermittent painless epistaxis for 1 year	No imaging reported. During operation, found to be in the right superior meatus and ethmoid sinus.	- Primitive cells with hyperchromatic nuclei arranged in sheets or a lobular pattern with focal neural fibrils. - Flexner-Wintersteiner and Homer Wright rosettes noted. - Moderate nuclear anaplasia and sparse mitotic figures. - Submandibular lymph node showed metastatic olfactory neuroblastoma.	Typical olfactory neuroblastoma: +NSE, S-100, synaptophysin, chromogranin. Craniopharyngiomatous portion: cytokeratin-reactive. Tumor cells of olfactory neuroblastoma: non-reactive for ACTH, somatostatin, and calcitonin.	Olfactory neuroblastoma, grade II
Sato et al (1997) 11	30-Year-old man with history of left submandibular mass 5 months prior presents with left nasal obstruction and hyposmia	Mass in left nasal cavity occupying ethmoid sinus without bone destruction	- Small round nuclei and indistinct cytoplasmic borders in neurofibrillary background. - Gland-forming tumor cells.	Neuroblastoma: +NSE and neurofilaments Adenocarcinoma: +CEA	Mixed olfactory neuroblastoma
Miller et al (1984) 12	77-Year-old man with right nasal obstruction and occasional epistaxis	Mass in right nasal cavity deviating the septum to the left, eroding the upper septum, opacifying maxillary and ethmoid sinuses bilaterally, protrusion into the nasopharynx	- Sheets and large nests of small, round to oval cells with scant cytoplasma - Pale and oval nuclei with prominent and often multiple nucleoli and frequent mitotic figures. - Nests of cells surrounded by edematous myxoid mucinous stroma with collagen and blood vessels. - Multiple small scattered foci of tumor necrosis. - Larger cells with abundant and amphophilic cytoplasm, with multiple nuclei. - Small anaplastic cells with fibrillar network with occasional single large polygonal cells with large nuclei, prominent nucleoli, and basophilic cytoplasm. - Sharply circumscribed islands or nodules of larger cells with large vesicular nuclei arranged in cribiform acinar pattern and some necrotic debris.	Neurofilament immunocytochemistry stained occasional peroxidase-positive processes. +Mucocarmine presents in apical portions of some foci.	Neuroblastoma with focal differentiation into ganglioneuroblastoma and adenocarcinoma

NSE, neuro-specific enolase.

Case Presentation

An 85-year-old man with an unremarkable medical history presented to the otolaryngology clinic with increasing epistaxis, which upon workup revealed a right-sided sinonasal mass. Non-contrast sinus computed tomography and contrasted magnetic resonance imaging demonstrated a right nasal mass, arising from the olfactory cleft and anterior skull base involving the nasal bones with no significant intracranial or orbital extension (Figure 1A-D). An initial endoscopic biopsy of the mass was reported as an infiltrative malignant tumor with neuroendocrine differentiation. The patient underwent resection of the tumor via an extended endoscopic approach including an open lateral rhinotomy to remove the involved nasal bone and undergo reconstruction (Figure 2A). Reconstruction of the nasal bone was accomplished with a titanium plate (Figure 2B) and a pedicled nasoseptal flap (not shown).

Figure 1.

CT scan (A, B) showing right sinonasal mass with erosion of nasal bone and septum. MRI with contrast (C) and T2 image (D) showing a mass arising from the olfactory cleft and anterior skull base, but no significant orbital or intracranial extension.

Figure 2.

(A) The lateral rhinotomy approach to resect the tumor involving the nasal bone, and (B) endoscopic titanium plate reconstruction for the nasal bone after tumor resection.

Histologic and Molecular Profile

Pathology assessment revealed a biphenotypic tumor. The majority of the tumor demonstrated histologic findings consistent with ON, including small round or oval blue cells arranged in nests and ribbons with Flexner-Wintersteiner rosettes (Figure 3A). The tumor cells in this region had a high nuclear:cytoplasmic ratio, with coarsely stippled chromatin, abundant apoptoses, and mitoses. Immunohistochemical staining in this region showed positivity for chromogranin, synaptophysin, and CD56. The minority region was composed of moderately to well-differentiated epithelial cells with mucocytes and gland formation, nonreactive to neuroendocrine markers, indicating divergent differentiation (Figure 3B-D). Immunohistochemistry did not show loss of INI1 expression and in situ hybridization for Epstein Barr virus was negative. Patchy reactivity was seen for p53, and background structures were stained for CK5/6, p63, and p40 as appropriate. A Hyams grade of 3 was determined from histological findings, and Kadish stage of C was chosen because of tumor extension into the paranasal sinuses.

Figure 3.

(A) Small blue cells with abundant apoptosis and Flexner-Wintersteiner rosettes. (B) Gland-like formations with goblet cells and mucin. (C) Synaptophysin highlighting a subset of cells. (D) Mucicarmine stain highlighting mucin pink.

Tumor tissue was sent for NGS at the University of Florida Health Pathology Laboratories. Genomic DNA extracted from the tissue was amplified using the GatorSeq NGS Panel and sequenced on the Illumina NextSeq. The sequence was processed using the genomic analysis application DRAGEN enrichment version 3.9.5 (GenomOncology LLC, Cleveland Ohio, USA), designed to accurately detect base substitutions, insertions, deletions, and copy number variations. NGS revealed a pathogenic mutation in PIK3CA (3140A>T) and a pathogenic variant in RUNX1 (AML1). Other detected genetic variants of unknown significance included CD276, ATM, NCOR1, PIK3R2, DOT1L, AXL, POLD1, SEC23B, LRP1B, CUL3, and MAGI2.

The patient underwent an uneventful surgical recovery and adjuvant treatment involved radiation therapy. Chemotherapy was considered but not recommended due to the patient’s advanced age.

Discussion

ON with multiple differentiation patterns is a very rare entity within primary sinonasal tumors with only 7 cases reported in the literature to date (Table 1). Treatment guidelines for ON have remained largely unchanged with surgical resection as the standard of care. There is an opportunity to update our understanding as recent studies suggest that postoperative chemotherapy improves survival, especially for high-grade tumors. ¹³ Often, this is decided on a case-by-case basis; consequently, clinicians and patients would benefit from an updated protocol regarding postoperative chemotherapy. ⁸

To advance therapy and understand the prognosis for this patient population, we suggest scrutinizing the current tools used to characterize the features of ON, such as the Hyams grading system, the Kadish staging system, and immunohistochemistry markers. There is limited available evidence of the utility of the Hyams and Kadish systems. Some studies demonstrate that they provide some benefit in understanding prognosis and disease progression.^14,15 However, these studies do not include ON with divergent differentiation, which limits their generalizability. Immunohistochemistry markers such as chromogranin, S100, and synaptophysin are used by convention but have not consistently predicted clinical outcomes for patients with ON. ⁴ There is a need for tools that can account for additional tumor characteristics, including those with divergent differentiation. A molecular methodology like NGS has the ability to fill this gap.

Here, we present the use of NGS in ON with divergent differentiation for the first time. Our histological findings showed alteration in TP53, PIK3CA, CDKN2A, and CDK2NC, which have been previously described in the literature on genomic alterations in ON without divergent differentiation. ¹⁶ Each of these proteins has targeted chemotherapeutics available, although none have been specifically indicated for ON. We additionally found mutations in RUNX1 (AML1), which is a transcription factor that acts as a tumor suppressor in myeloid and breast cancers. This demonstrates one of the key advantages of NGS—its ability to provide insight at the nucleotide level, which facilitates a more detailed interrogation of the tumor genome. We encourage clinicians to incorporate NGS into the routine work-up for patients with this rare tumor because it may reveal more detailed information about the tumor genotype and contribute to the research community’s effort to better characterize the ON genetic landscape. ¹⁷ As genetic evidence grows, we can move closer to potential future therapeutics and unveil the molecular mechanisms driving divergent differentiation. ¹⁸

Conclusion

ON with divergent differentiation is a rare tumor with varying pathological features. Leveraging NGS can expand our understanding of this rare tumor and potentially deliver more personalized treatment to patients with ON with divergent differentiation.