Intrasellar and parasellar cellular schwannoma.

The complexity of the anatomy of the sella turcica and its surroundings accounts for the large number of pathologic entities that may involve this critical area. Intrasellar and parasellar schwannomas are exceedingly rare; only a handful of true sellar tumors of this nature have been reported in the English literature. These lesions may simulate nonsecretory pituitary adenomas clinically and neuroradiologically. Although benign, complete surgical resection of these tumors is usually difficult because of their size, invasiveness, and rich vascularity. From the histopathologic stand point, those cases lacking typical schwannoma histomorphologic features may pose a diagnostic challenge to the pathologist, especially at the time of frozen section examination, because they may resemble other spindle cell neoplasms more common to that location, such as fibrous meningothelial tumors. We report a case of intrasellar and parasellar cellular schwannoma lacking common and reliable neurilemmomatous features, such as the coexistence of cellular Antoni A and loose Antoni B areas, Verocay bodies, and hyalinized thickened vessels. In addition, features infrequently seen in schwannomas were identified in the specimen, including the presence of psammoma bodies, nuclear optically clear pseudoinclusions, and fine intracytoplasmic melanin-like pigment. Ultimately, the use of immunohistochemistry was necessary to achieve a definitive pathologic diagnosis. Cellular schwannoma expands the pathologic differential diagnosis of spindle cell neoplasms of sellar location that the pathologist should have in mind, especially at the time of frozen section examination. The clinical, histopathologic, and neurosurgical aspects of primary cellular schwannomas of the sella turcica are reviewed.