Esthesioneuroblastoma pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Simrat Sarai, M.D. [2]
Overview
Pathophysiology
Gross Pathology
Arises from olfactory mucosa - upper nasal cavity
Microscopic Pathology
- Small round (blue) cell tumour with:
- Stippled chromatin.
- High NC ratio.
- +/-Flexner-Wintersteiner rosette - rosette with empty centre (donut hole).
- +/-Fibrillary, eosinophilic material (neuropil-like)
Olfactory neuroblastomas are of neural crest cell origin. They are mulilobulated pink-grey tumors. Histology demonstrates variable differentiation, from well formed neural tissue to undifferentiated neuroblasts with pseudorosette formation 2. It has been suggested that olfactory neuroblastoma is actually part of the Ewing sarcoma group of tumors, rather than being related to neuroblastoma.
Olfactory neuroblastomas are of neural crest cell origin 1. They are mulilobulated pink-grey tumours.
Histology demonstrates variable differentiation, from well formed neural tissue to undifferentiated neuroblasts with pseudorosette formation 2. It has been suggested that olfactory neuroblastoma is actually part of the Ewing sarcoma group of tumours, rather than being related to neuroblastoma
On gross examination, biopsy material from olfactory neuroblastoma is soft and hemorrhagic. Resection specimens may show a polypoid appearance. Microscopically, the tumor grows beneath the surface respiratory epithelium and may produce focal ulceration. The vascular supply is rich and fragile, accounting for the hemorrhagic gross appearance.
In low-grade (well-differentiated) lesions, the growth pattern is lobulated with transitions into sheets or discrete nests of tumor cells, which are small and round with high nuclear cytoplasmic ratios (picture 1) [21,22]. In well-differentiated tumors, the nuclei show uniform chromatin distribution with small inconspicuous nucleoli. The nuclei become progressively more pleomorphic, with coarse chromatin clumping and prominent nucleoli, with increasing tumor grade. The stroma in well-differentiated tumors is distinctly fibrillary, reflecting the neuronal (axonal) processes made by the tumor cells. This stroma decreases in quantity as the tumor becomes less well-differentiated. Mitoses and areas of necrosis also become more frequent with increasing tumor grade.
Homer Wright pseudorosettes, which are composed of tumor cells surrounding a center of pink fibrillary material, are seen in one-half of olfactory neuroblastomas; true (Flexner type) rosettes, composed of tumor cells surrounding a central lumen, are best seen in higher grade tumors. Necrosis, dystrophic calcification, and vascular or lymphatic invasion are more common with increasing tumor grade. In rare instances, a few admixed ganglion cells may be present. Electron microscopy of olfactory neuroblastomas demonstrates numerous axonal-type cytoplasmic processes, which contain neurofilaments, neurotubules, and dense-core neurosecretory granules (100 to 200 nm in diameter) [21,22]. The S100 immunoreactivity corresponds to Schwann cells enveloping cell bodies and axonal processes (see 'Differential diagnosis' below).
The Hyams histologic grading system grades tumors from I to IV based upon pathologic features such as mitotic activity and necrosis [21].
●Grade I tumors are characterized by a prominent fibrillary matrix, tumor cells with uniform nuclei, absent mitotic activity, and necrosis. ●Grade II tumors have some fibrillary matrix and exhibit moderate nuclear pleomorphism with some mitotic activity. There is no necrosis. ●Grade III tumors have minimal fibrillary matrix and Flexner type rosettes are present. There is more prominent mitotic activity and nuclear pleomorphism, and some necrosis may be seen. ●Grade IV tumors have no fibrillary matrix or rosettes and show marked nuclear pleomorphism and increased mitotic activity with frequent necrosis. Most studies have found a correlation between Hyams grade and prognosis [13,17,21,23]. In a meta-analysis that included five studies in which lesions were graded histologically, the mean five-year survival was 56 percent for those with low-grade lesions (Hyams I and II) versus 20 percent for those with high-grade lesions (Hyams III and IV) [23]. However, a SEER study of 281 patients treated from 1973 to 2010 showed that patients with grade I and II tumors had a 10-year overall survival rate of 67 percent and those with high grade tumors (III and IV) had a 10-year overall survival rate of 34 percent. For high-grade tumors, multivariate analysis showed Kadish stage predicted for worse disease-specific survival and radiation independently predicted for improved disease-specific survival (B-Tajudden).
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Associated Conditions
- Associated with Trisomy 8.