Olfactory neuroblastoma

Abstract

Few neoplasms are unique to the sinonasal tract, but sinonasal undifferentiated carcinoma and olfactory neuroblastoma are malignant tumors which require unique management. Due to the rarity of these tumors, practicing pathologists are not always aware of their distinctive clinical, radiographic, histologic, immunohistochemical, and molecular features. These cases are frequently submitted for consultation, further suggesting the diagnostic difficulties inherent to these tumors. Specifically, olfactory neuroblastoma is a neoplasm that can histologically mimic many tumors within the sinonasal tract, making recognition of this tumor important, as the management frequently requires a bicranial-facial surgical approach, a trephination procedure which can be quite technically difficult and challenging to achieve a good result. The management is therefore quite unique in comparison to other sinonasal tract malignancies, setting it apart diagnostically and managerially from other lesions.

Fig. 1

An MRI shows a mass expanding and filling the upper portion of the nasal cavity, extending through the cribriform plate (arrow), showing early intracranial extension

Fig. 2

This polypoid projection shows an intact respiratory epithelium. There are lobules or islands of tumor in the edematous stroma

Fig. 3

A low power magnification demonstrates numerous lobules or islands of interconnecting tumor cells. There is a fibrotic to edematous vascularized stroma in the background

Fig. 4

There is a sheet of neoplastic cells with a very high nuclear to cytoplasmic ratio. The cells are arranged in a syncytium. The nuclear chromatin is even to delicate in this Grade I tumor

Fig. 5

Anisocytosis and anisonucleosis is noted in this Grade II lesion. Areas of pyknosis are also present. However, there is still a lobular architecture maintained

Fig. 6

There is quite a bit of pleomorphism with easily identified prominent nucleoli in this Grade III tumor. Note the suggestion of a Flexner-Wintersteiner rosette

Fig. 7

The tumor nests are arranged in small pseudorosettes with faint eosinophilic, fibrillar material in the center of pseudorosettes. There is a vascularized stroma

Fig. 8

There are numerous “duct-like” spaces with non-ciliated columnar cells arranged around a central lumen: these are Flexner-Wintersteiner rosettes in a Grade III neoplasm

Fig. 9

Tumor necrosis (lower part of field) and a lack of organoid growth are noted in this Grade IV ONB

Fig. 10

Chromogranin yields a granular reaction in the cytoplasm of the neoplastic cells, giving a variable reactivity in each tumor cell

Fig. 11

CD56 gives a strong and heavy membrane-type staining

Fig. 12

A delicate sustentacular reaction with S-100 protein (nuclear and cytoplasm) highlights the supporting framework cells of an ONB