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Image of the Week
Edited and moderated by Stacey Mills, MD, Pathology Network's Image of the Week Blog is a forum for the discussion of interesting and often diagnostically challenging pathology images.
Friday, October 04, 2013
A 45-year-old woman with a polypoid nasal mass.
A 45-year-old woman presented with a polypoid nasal mass.  The exact location in the nasal cavity was not specified.  The patient underwent a biopsy and the resultant specimen is illustrated below.
Beneath attenuated but intact surface mucosa are irregular but sharply demarcated nests of epithelioid cells with enlarged, uniform nuclei and clearly visible nucleoli.  There is no evidence of glandular or squamous differentiation.  There is no necrosis.  Mitotic figures are easily found but are not abundant. 
What is your diagnosis?
Immunohistochemical studies were performed.  The tumor was negative for epithelial markers.  Results of immunohistochemical studies for S100 protein, calretinin and synaptophysin are shown below (in that order).
The cells surrounding the tumor nests are strongly positive for S100 protein, but the epithelioid cells within the nests themselves are negative.  In contrast, the neoplastic epithelioid cells are strongly positive for calretinin, synaptophysin and chromogranin (not shown).
This is a nice example of an olfactory neuroblastoma (ONB). 
These tumors virtually always arise from the superior nasal cavity, presumably from olfactory type cells or olfactory "inclined" stem cells in this region.  Often they appear
as a vascular, polypoid mass.  Involvement of the cribriform plate and direct extension in to the cranial cavity through the plate is common.
ONBs show considerable variation in their microscopic appearance, including the presence of Homer Wright type rosettes, and divergent glandular differentiation. The current example is at the "low grade" end of the spectrum, although we have not found grading these tumors to be of clinical value, as long as sinonasal undifferentiated carcinomas (SNUCs) are clearly separated from lesions considered to be high-grade ONBs. 
ONBs typically show little or no cytokeratin positivity and strong positivity should lead to other diagnostic considerations.  When the tumors form nice cell nests, as in this case, the presence of S100 positive sustentacular cells around the periphery of the nests is diagnostically helpful.  Similar cells may be seen surrounding other neural or neuroendocrine-type lesions including paragangliomas and neuroblastomas.  The prominent thick-walled capillaries seen in the second H&E image above are also characteristic of this tumor. 
Prognosis for ONB is good if the lesions can be completely excised.  Long-term followup is required, however, as recurrences and metastases have been documented after decade-long disease free intervals.
Dr. radha ananthakrishnan MD said:
Thank you for a good case,Sir. How do we differentiate this from a paraganglioma using IHC ? [Dr. Mills sez: You basically don't see paragangliomas high in the nasal cavity, as opposed to in the middle ear or along the carotid or vagus nerve. They really don't look the same microscopically, though both may be nested. ONB may show some chromogranin positivity but paragangliomas should be STRONGLY positive. Paragangliomas should show no epithelial differentiation, but ONB's often show at least a little. I've really never enountered this as a diagnostic dilemma. The cell types are fundamentally different.]
Rosana Eisenberg said:
Dear Dr. Mills: Isn't the 2nd IHC supposed to be calretinin rather than calcitonin? [Dr. Mills Sez: You are, of course, absolutely correct. Written in a hurry without good proofing! I've updated the blog. Nice to see someone reads it carefully! Thanks!]
About the Author

Stacey E. Mills, MD
Stacey E. Mills, MD, a graduate of University of Virginia (UVA) and the UVA Medical Center, has authored nearly 230 articles, 20+ books, atlases and monographs—including the renowned Sternberg's Diagnostic Surgical Pathology. He has been a practicing Professor and Staff Pathologist at UVA for 30+ years and is Director of Surgical Pathology and Cytopathology. His clinical specialty is general surgical pathology with emphasis on neoplasms and neoplasm-like lesions. Dr. Mills is also Editor-in-Chief of The American Journal of Surgical Pathology.