Inflammatory malignant fibrous histiocytoma of the kidney: an immunohistochemical and ultrastructural study.

A primary inflammatory malignant fibrous histiocytoma of the kidney is reported. The differential diagnosis from other sarcomas and pseudosarcomatous lesions is discussed on the grounds of the histologic, immunohistochemical and ultrastructural results. The neoplasm was made up of histiocytes, fibroblasts, myofibroblasts, foam cells and undifferentiated mesenchymal cells with admixed granulocytes, lymphocytes and plasma cells. The immunohistochemical study showed a positivity for alpha-1-antichymotrypsin and a weak positivity for alpha-1-antitrypsin in mononuclear and pleomorphic multinucleated tumor cells. PAS-positive, diastase-resistant intracytoplasmic hyaline globules in necrotic cells, examined by electron microscopy, most likely represent lysosomal structures, in accordance with the theories of De Duve, Vattiaux and Von Ardenne.