Answer: Nasal glioma

Histology: The lesion consists of a polypoid mass with alternating dense collagen bundles with lighter pink, delicate, fibrillary stroma resembling neuropil. The individual nuclei are small, ovoid to stellate and bland. No mitoses are identified.

Discussion: Nasal glial heterotopia (nasal glioma) is a non-neoplastic proliferation of glial cells that can either present as a subcutaneous mass on the bridge of the nose, or as a mass inside the nasal cavity. True glial heterotopia does not actively communicate with the central nervous system, that is, it is not an extension of an encephalocele (which as a separate entity can protrude into the nasal cavity or sinuses), although some consider it to be a variant of a congenital encephalocele. The glial component may be difficult to distinguish from sinonasal stromal collagen/connective tissue, and an intra-nasal glioma may be mistaken for a nasal polyp, but the glial component can be highlighted with immunostains for GFAP (glial fibrillary acidic protein) or S100. Occasionally, neurons can be identified in the neuropil. Surgical excision is typically curative.

Neurofibromas are benign nerve sheath tumors which contain all components of the nerve sheath (Schwann cells, axons, perineurial cells, etc) and are patchy positive for S100 protein; granular cell tumors are benign neoplasms consisting of polygonal cells with abundant granular cytoplasm that label for S100 protein and CD68.

Reference(s):
– Kardon DE. Nasal glial heterotopia. Arch Pathol Lab Med. 2000 Dec;124(12):1849.
– Penner CR, Thompson L. Nasal glial heterotopia: a clinicopathologic and immunophenotypic analysis of 10 cases with a review of the literature. Ann Diagn Pathol. 2003 Dec;7(6):354-9.