Answer: Esthesioneuroblastoma (ENB), high grade

Histology: The tumor demonstrates a predominant solid pattern of growth. The tumor cells are somewhat pleomorphic, and mitotic figures are plentiful. Tumor necrosis is focally present. The tumor does not exhibit a neurofibrillary stroma, but subtle rosette formations can be appreciated. Shown is a synaptophysin immunostain, which is positive.

Discussion: Esthesioneuroblastoma (i.e. olfactory neuroblastoma) is an uncommon neoplasm that is believed to arise from the reserve cells of the olfactory epithelium. Accordingly, they usually arise from superior/posterior portion of the nasal cavity. They occur over a wide spectrum of ages, showing a bimodal distribution at 15 and 55 years of age. Presenting signs are non-specific, usually consisting of unilateral nasal obstruction and epistaxis.

The role of histologic grading for prognostication is controversial. Many believe that tumor staging is more predictive of survival. In any event, a grading scheme proposed by Dr. Hyams uses a 4-tiered system that takes into account architecture, mitotic rate, degree of pleomorphism, and the presence or absence of neurofibrillary stroma and rossetts. Those morphologic features that are important in establishing a diagnosis of ENBs are not very apparent in those tumors that are poorly differentiated (i.e. grade 4). In particular, high-grade ENBs typically lack a neurofibrillary stroma and a lobular pattern of tumor growth, and thus may be difficult to distinguish from other poorly differentiated tumors of the sinonasal cavity. In these instances, an immunohistochemical panel that includes synaptophysin can be helpful in establishing the neuroepithelial nature of the tumor.

ENBs are generally treated by surgical resection, often combined with radiation. Patient survival varies according to tumor stage, ranging from 90% at 5 years with stage 1 disease to 47% at 5 years with stage 3 disease.