A 76-year-old male with chronic sinusitis presents for evaluation of 6 months of ongoing epistaxis and anosmia. He reports a history of a hematologic malignancy and a remote left thalamic infarct leading to right hemiparesis and hemiplegia.

Head CT shows a polypoid mass in the left anterior skull base:

Left anterior skull base

Following nasal endoscopy and diagnostic biopsy, resection of the mass and anterior skull base was performed.

Histologic sections of the resection show the following:

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Histologic sections of the resection

Histologic sections of the resection

Histologic sections of the resection

Histologic sections of the resection

Histologic sections of the resection

Histologic sections of the resection

Immunohistochemical studies were performed:

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Synaptophysin

Chromogranin

S100

Tumor cells show negative staining for AE1/AE3, CD45, and HMB45.

The most likely diagnosis is:





 

The correct answer is:

 

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