Imaging and surgical pathology were initially consistent with an L5 schwannoma including spindle morphology without mitoses and retained S100 expression.
Findings from the statistical analyses suggested duration of preoperative symptoms, Sridhar classification, tumor size, bone damage, Ki67 labeling index, and S100 expression were different between benign schwannoma and the malignant subtype.
Histopathology confirmed these lesions as schwannomas consisting of areas of Antoni A and B, and immunohistochemical study was positive for S-100 protein.
GISTs were defined as c-kit (CD117)-positive tumors, leiomyomas as desmin-positive and c-kit-negative tumors, and schwannomas as S-100-positive and c-kit-negative tumors.
The tumors differ from ordinary leiomyomas and schwannomas in several respects: the GISTs typically express c-kit protein (CD117) and CD34, 30% to 50% of them are (often focally) positive for alpha-smooth muscle actin, and all are negative for desmin and S100 protein.