Pseudoglandular elements in schwannomas.

CONTEXT: Uncommon examples of schwannomas are seen in which a coexisting glandular component is present. The pseudoglandular schwannoma is a relatively recently described variant in which cystic spaces are lined by pseudocolumnar or cuboidal-like neoplastic Schwann cells exhibiting an epithelial-like appearance. OBJECTIVES: To determine the incidence of pseudoglandular elements in schwannomas, to describe the variable morphology of the schwannomas that may contain pseudoglandular elements, and to discuss the potential mechanisms of development and biological significance of these elements. DESIGN: We screened 202 schwannomas from any anatomic site for the presence of pseudoglandular elements and examined these with light microscopy, immunohistochemistry, and electron microscopy. RESULTS: Sixteen (7.9%) of the schwannomas contained pseudoglandular elements, which ranged from poorly to well organized in appearance and which were found in schwannomas exhibiting a wide range of morphologic appearances. The Schwann cell nature of the cells composing these elements was apparent both immunohistochemically and ultrastructurally. The frequency of proliferative activity within these elements was no greater than that observed throughout the remainder of the respective schwannomas. CONCLUSIONS: Our observations suggest that, rather than representing a distinct phenotypic schwannoma variant, pseudoglandular elements likely arise as a response to a degenerative phenomenon, perhaps reflecting the propensity that the Schwann cell has to palisade formation. Such elements may be found within a variety of schwannoma variants and do not appear to possess a unique growth potential.