Nasal glioma mimicking an astrocytoma: case report

Ear, Nose & Throat Journal, Oct, 2005 by Ali Amin, Ahmad Monabati, Perikala V. Kumar, Seyed Baseer Hashemi

Abstract

Nasal glioma is a rare benign tumor that usually occurs during infancy. We report a case of nasal glioma in a 6-month-old boy in which the histomorphologic features resembled those of an anaplastic astrocytoma.

Introduction

Nasal glioma is a displaced, mature, neuroglial tissue that has no connection to the brain (hence it is called heterotopia). It is a rare glial tumor that usually appears submucosally as a pedunculated mass in the midline, attached to the nasal septum. Most cases are identified at birth or soon thereafter. No sexual predilection has been observed.

There is general agreement on the outcome of the tumor, as long-term follow-up of patients has revealed no recurrence or tumor invasion into adjacent tissues. Simply said, the tumor is benign despite the presence of minor microscopic abnormalities that might be seen. Some cases may feature bony defects of the cranium and a concomitant brain tumor. No universal agreement exists as to the true origin of the tumor. All previously reported cases of primary nasal glioma were characterized by mature glial features. The new case we report appears to be the first that has featured atypical microscopic morphology but benign behavior.

Case report

A 6-month-old boy was brought to us for evaluation of nasal obstruction, rhinorrhea, failure to thrive, and feeding and sleeping difficulties; these conditions had been present since his birth. General physical examination revealed that the infant was undernourished and that he had a large pedunculated mass in the left nostril. Magnetic resonance imaging (MRI) revealed that the mass had no connection to brain tissue (figure 1). There was no bony defect or concomitant brain tissue pathology.

[FIGURE 1 OMITTED]

The patient underwent total excision of the pedunculated mass via an endonasal approach, followed by catheterization of the base of the mass to stop bleeding. On gross examination, the mass was creamy-gray and soft, and it measured 3 x 1 x 1 cm.

Microscopic evaluation revealed that the surface of the polyp-like tumor contained upper respiratory mucosa. Beneath the surface was a rather hypercellular tumor in a neurofibrillary background; this tumor was separated from the overlying mucosa by a loose edematous stroma. The mass was well vascularized and featured areas of microcystic formation and microcalcifications (figure 2, A). Also present was a polymorphic population of cells with consistently round-to-oval irregular nuclei; some of the cells were hyperchromatic and some were vesiculated. Some foci had gemistocyte aggregation and a few ganglion cells that were accompanied by mild infiltration of chronic inflammatory cells throughout (figure 2, B). A few nasal mucosal glands were trapped within the tumor tissue; chronic inflammatory cells cuffed around them and around the vessels. Mitoses were rare, and none was atypical. We found no evidence of any neuronal tissue or any fibrosis in sections. Immunohistochemistry for glial fibrillary acid protein (GFAP) and S-100 protein showed diffuse positivity in the tumor cell cytoplasm.

[FIGURE 2 OMITTED]

While some of our findings (e.g., mitoses) favored a diagnosis of an astrocytoma, the overall histologic features (e.g., the polymorphic background population of the cells and the presence of many reactive cells) guided us to identify the tumor as a benign lesion.

Discussion

According to our review, only 12 cases of nasal glioma have been previously reported in the literature. Most occurred in infants; the few exceptions involved middle-aged adults. The older patients frequently had cranial bone defects, congenital anomalies, brain tumors, or glial heterotopias with malignant features. (1-3)

The differential diagnosis of a nasal neuroglial mass in an infant is narrow. The most likely possibility is the presence of an encephalocele, with or without brain attachment. (4) Encephaloceles can often be differentiated by considering the presence of meningeal tissue surrounding the tumor and less often by the presence of bony defects. (5,6) Other differential diagnoses include intracranial astrocytoma or meningioma with nasal extension, neuroglial heterotopia, lymphoma/plasmacytoma, esthesioneuroblastoma, angiofibroma, lethal midline granuloma and, rarely, carcinoid tumor. Some of these tumors are rarely seen in infancy (i.e., esthesioneuroblastoma and angiofibroma), and others can be excluded by histopathology and immunohistochemistry.

The least common differential diagnosis is metastasis or direct invasion of an intracranial astrocytoma, which is often very difficult to differentiate from nasal glioma. This rare finding is mostly observed in the elderly. (2)

Imaging can be used to look for probable concomitant intracranial tumors and the existence of a connection between a cranial and nasal tumor. In light of our radiologic and histopathologic findings, we identified the mass in our patient as a neuroglial heterotopia, which is defined as a hypervascular neuroglial tumor with diffuse areas of fibrosis. Isimbaldi et al reported mild atypical changes in this tumor. (3) The tumor we describe belongs in this category, although our case is unique in view of our distinguishing findings of the absence of fibrosis and neuronal tissue and the presence of abundant gemistocytes, mild vascular proliferation, perivascular cuffing, mild cellular anaplasia, and mitoses. Long-term follow-up of patients has proved that their behavior is benign following complete excision. (7)