Olfactory Neuroblastoma
Olfactory neuroblastoma The use of microscopes in microsurgery is critical to aide the surgeons during the actual surgery. Olfactory neuroblastoma or esthesioneuroblastoma is an uncommon malignant neuroectodermal nasal tumor that accounts for approximately five percent of all malignant neoplasms. Olfactory neuroblastomas are thought to arise from the specialized sensory neuroepithelial olfactory cells that are normally found in the upper part of the nasal cavity, usually including the cribriform plate of the ethmoid sinus. These tumors affect both sexes equally. A bimodal age distribution has been documented, although patients of all ages can be affected. Patients present with nonspecific symptoms of nasal obstruction of cinseventy percent of the cases and epistaxis with fifty percent; less common symptoms include headache, pain, visual disturbances, and anosmia with less than five percent. Owing to the nonspecific nature of the presenting symptoms, patients often have a long history prior to diagnosis.
One of the characteristic radiographic findings of olfactory neuroblastoma is a dumbbell shaped mass that extends across the cribriform plate; erosion of the cribriform plate, lamina papyracea, and/or fovea ethmoidalis may also be seen. T1 weighted magnetic resonance imaging with gadolinium contrast will show marked enhancement. For practical purposes, all olfactory neuroblastomas involve the cribriform plate to some degree or other. Even though the bulk of a tumor may lie intracranially, it is still attached to the cribriform plate. Microscopically, one of the most reliable histologic features is a lobular architecture. Circumscribed lobules or nests are made up of primitive neuroblastoma cells, usually below an intact mucosa and in a vascularized fibrous stroma. The tumor cells are small, round, and blue; they are slightly larger than mature lymphocytes; and they have a high nucleus to cytoplasm ratio. The cells are often arranged in a syncytial pattern, with a tangle of neuronal processes forming the background.
The nuclei are small and uniform with an even distribution of granular nuclear chromatin. Nucleoli are inconspicuous. For the most part, nuclear pleomorphism, increased mitotic figures, and necrosis are uncommon. Olfactory neuroblastomas are graded I through IV on the basis of the degree of differentiation and the presence or absence of a neural stroma, mitotic figures, and necrosis. Higher-grade tumors are less differentiated, and pseudorosettes and fibrillar stroma are less common. The nuclei become more pleomorphic, chromatin is coarser, mitotic figures increase, and tumor necrosis is present. The grade correlates with the prognosis, although not as closely as does tumor stage; stage A tumors are limited to the nasal cavity, stage B tumors involve the nasal cavity and paranasal sinuses, and stage C tumors extend beyond these structures. Approximately one-half of all olfactory neuroblastomas are stage C tumors at presentation.
Owing to the small, round, blue cell nature of the neoplasm, the differential diagnosis is quite broad; it includes melanoma, rhabdomyosarcoma, sinonasal undifferentiated carcinoma, lymphoma, Ewings sarcoma, pituitary adenoma, plasmacytoma, paraganglioma, and primitive neuroectodermal tumor. Clinical and demographic findings can help make distinctions, as can pertinent immunohistochemical reactions to synaptophysin, chromogranin, neuron-specific enolase , neurofilament protein, S 100 protein, keratin, CD45RB, desmin, CD99, and HMB45. Olfactory neuroblastomas are usually positive with synaptophysin, chromogranin, NSE, NFP, and S-100 protein. Radical surgical eradication combined with radiotherapy is the gold standard of care. In a few selected cases, endoscopic resection with adjuvant radiation may have merit.
