Answer: Nasal glioma

Histology: The specimen consists of a firm smooth polypoid mass. The submucosa is filled and expanded by irregular lobules of pink fibrillary material that is intersected by bands of
fibrous tissue. Embedded within the fibrillary matrix are cells with round oval nuclei and abundant pink cytoplasm. Throughout much of the lesion, the bands of collagen compress the lobules into thin and irregular cords. The fibrillary processes are GFAP and S100 positive (see below). Dura and meninges are not identified.

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Discussion: Glial heterotopia (“nasal glioma”) results from congenital displacement of central nervous tissue in or about the nose, probably as a result of the frontal lobe to completely retract through the foramen cecum during fetal development. About 25% of these lesions retain communication with the central nervous system (usually by a fibrous stalk). Nasal gliomas are usually apparent during the first year of life. Intranasal masses (as opposed to subcutaneous masses) generally present as respiratory distress, nasal obstruction, epistaxis or cerebrospinal fluid leakage.

Histologically, nasal gliomas are composed of astrocytes and neuroglial fibers. Neurons tend to be absent or sparse. The finding of abundant neurons should raise the possibility of a true encephalocele. An intersecting fibrovascular stroma is a consistent finding, and in long-standing
cases this connective tissue can override and obscure the glial tissue. In these instances, immunohistochemical stains for GFAP and S-100 are useful in highlighting the glial tissue. Although glial tissue may also be encountered in nasopharyngeal teratomas, teratomas (unlike nasal gliomas) also harbor tissues from the other 2 germ cell layers. The main differential diagnosis of a nasal
glioma is a true encephalocele. The presence of dura and/or leptomeninges confirms the diagnosis of an encephalocele. A head and neck mass in young children and comprised of cells with abundant pink cytoplasm may also bring to mind congenital granular cell tumor (congenital epulis) and rhabdomyoma, but these can be easily excluded on clinical grounds (e.g. congenital epulis arises exclusively from the ginigiva and rhabdomyomas usually arise from the soft tissues of the neck) and histologic appearances. In long standing cases of nasal glioma, the fibrous stroma may distort the appearance of the glial tissue and cause confusion with some mesenchymal tumor such as neurofibroma. In cases
where the diagnosis is in doubt, documentation of the neuroglial nature of the cells using a GFAP immunostain will establish the diagnosis of glial heterotopia.

The term “nasal glioma” is a misnomer. These are the result of tissue displacement, not neoplasia. Accordingly, surgical removal is curative.