Analysis of Peripheral Nerve Schwannoma Pseudocapsule

Using proper surgical technique, schwannomas can be resected safely, with a low recurrence rate and high likelihood of improvement in symptomatology. There are multiple peritumoral tissue layers, and finding the correct plane is critical to safe tumor enucleation. The contents of the pseudocapsule tissue surrounding a schwannoma are not well described, and the consequences of resecting or leaving pseudocapsules are unknown.

An institutional database was searched for any pathology reports that contained both of the words "schwannoma" and "capsule." Charts and histopathologic specimens were reviewed to determine the contents of various tissue layers and determine if there was any correlation between pseudocapsular contents and clinical outcomes.

A pseudocapsule was separately sent for pathology in 36 patients during schwannoma resection. Ten pseudocapsule specimens contained microscopic foci of tumor. In a separate 6 patients, there was evidence of nerve fascicles. There were no correlations between the tumor or nerve in the pseudocapsule and postoperative neurologic deficits. After an average follow-up time of 3.1 years, no patients developed a recurrence either clinically or on follow-up imaging (imaging available in 52.7%). Histopathologically, the pseudocapsule was made of dense hypocellular collagen and occasionally contained arteries, veins, and nerve fascicles.

The pseudocapsule surrounding a schwannoma occasionally contained nerve tissue and blood vessels. While a microscopic focus of tumor was often found in this tissue layer, recurrence is exceedingly rare and did not occur in this case series. The risk of undue pseudocapsule dissection likely outweighs any negligible benefit from microscopic cytoreduction.