Abstract

Histopathologic and immunohistochemical analysis using antibodies for S-100 protein and keratin has been conducted on 21 cases of malignant schwannomas. The 21 cases were divided into the following three groups Group A: tumors originating from the nerve trunk or neurofibroma; Group B: tumors related to von Recklinghausen's disease; and Group C: other tumors not belonging to the above groups but histologically diagnosed as malignant schwannoma. The commonest histological pattern consisted of either closely packed or loosely arranged interlacing fascicles of slender spindle cells with wavy fibrillar cytoplasm, followed by myxoid change, perithelial pattern, hyaline change of the blood vessels, and hyalinlzed cords or nodules. Nine out of 12 cases of malignant schwannomas in group A and B, and 7 out of 9 cases of group C were positive for S-100 protein. None of the above cases showed positive staining reaction for keratin. Since 7 of 9 malignant schwannomas in Group C stained with S-100 protein, we can conclude that careful histological analysis supplemented by immunohistichemical study can make a conclusive diagnosis in most of the cases of malignant schwannomas even in cases that do not fulfil the traditional strict criteria.

• Keywords: Malignant schwannoma;Immunohistochemical staining;S-100 protein;Keratin