Sinonasal mucosa, bone, olfactory bulb and numerous nerves. The tissue is extensively infiltrated by cellular tumor forming lobules separated by thin blood vessels. Tumor cells have small round to oval nuclei with finely granular chromatin, small nucleoli and a moderate amount of wispy cytoplasm. No rosettes are identified. There is focal calcification. Mitoses are present but not prominent, with 3 per 10 hpf. Nuclear pleomorphism is moderate overall. There is no fibrillary matrix seen. There are areas of crush artefact but no convincing tumor necrosis. There are changes focal consistent with a previous biopsy.
By immunohistochemistry, the tumor cells are positive for calretinin, chromogranin, synaptophysin, and CD56 and negative for CAM5.2, CD99, AE1/3, HMB-45, Melan-A, desmin, CD99, CD45, CD3, CD20 and GFAP. S100 shows some sustentacular cells.