Primary sinonasal neuroendocrine carcinoma (SNEC) is a rare aggressive sinonasal malignancy which typically occurs in the ethmoidal or maxillary sinuses, with or without nasal cavity involvement, of middle-aged patients (median age 53 years), with a slight male preponderance. No risk factors have been identified. Most patients present at advanced stages due to the lack of significant symptoms.1,4,5,8 Advanced tumours may invade the skull, orbit or brain. Staging is of limited value in predicting prognosis and recent literature clearly highlights the importance of histological diagnosis, particularly differentiation grade, in determining the prognosis and predicting treatment response. Nomenclature has been ambiguous, but broadly SNECs can be classified as well-, moderately- or poorly differentiated. The latter group includes sinonasal undifferentiated carcinoma and sinonasal small cell carcinoma. On histological examination, well-to-moderately differentiated tumours show medium-sized cells with large nuclei containing stippled or ‘salt/pepper’ chromatin and scant cytoplasm. Nuclear moulding, increased mitoses and apoptotic bodies are commonly seen. Immunohistochemistry reveals expression of neuroendocrine markers.1,4–7 Poorly-differentiated tumours may lose expression of neuroendocrine markers and differentiation from other poorly differentiated malignancies can be extremely difficult.1,4–7 Due to the limited number of reported cases, there is no clear consensus on management, although oncologists now advocate multimodal therapy. Combined surgery and radiotherapy is thought to beneficial in moderately and poorly-differentiated subtypes.1,4–8 We describe a classical case of SNEC with secondary orbital involvement, with a review of the current literature.
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