Olfactory neuroblastoma. Cytodiagnostic features in a case with ultrastructural and immunohistochemical correlation

In a case of olfactory neuroblastoma, originally misdiagnosed as an undifferentiated carcinoma, cytologic examination of material scraped from the superior nasal vault revealed tumor cells suggestive of neuroblastoma. The most significant cytodiagnostic feature was the presence of a fibrillary cytoplasm with ill-defined borders. Also noteworthy were the smudged hyperchromatic nuclei and structures resembling rosettes or pseudorosettes. The diagnosis was confirmed by electron microscopy, which revealed the presence of dense-core neurosecretory granules, clear vesicles, neurotubules and neurofilaments, and by immunohistochemistry, which showed positive staining for neuron-specific enolase but negative staining for keratin and glial fibrillary acidic protein. Since olfactory neuroblastoma has a relatively good prognosis and aggressive surgical resection may be curative, it is important that this tumor be distinguished from other small cell malignancies arising in the nasal cavity. The present case shows that the diagnosis can be made by the cytologic examination of scrapings from the tumor.