Intranodal "amianthoid" myofibroblastoma. Report of six cases immunohistochemical and electron microscopical study.

Six cases of intranodal amianthoid myofibroblastomas are reported. Immunohistochemically the tumors were actin positive and S-100 protein and desmin negative. Intracytoplasmatic, actin-rich bodies, previously found to be a characteristic feature of this tumor, were identified as cytoplasmatic extensions filled with microfilaments at an ultrastructural level. Abortive vessel formation by the tumor cells and the proliferation of tumor cells centered on veins outside the capsule of the tumor in two of our cases indicated a close relationship between the intranodal palisaded myofibroblastoma and the musculature of vascular origin.