Diagnosis of tumors of the kidney: ultrastructural classification.

Diagnosis of tumors of the kidney depends principally on clinical evaluation and radiologic studies. The role of the pathologist is most important in the classification and characterization of the tumors. In addition, morphologic studies employing the use of electron microscopy may aid in the understanding of histogenesis and the recognition of tumor sub-types. Electron microscopic evaluation indicates specific cellular features characteristic of renal adenocarcinoma, nephroblastoma, and sarcomas. Ultrastructural examination can be particularly useful in distinguishing between sarcomas and sarcomatoid carcinomas and in identifying the origin of metastatic tumors. For these reasons, the use of electron microscopy for the evaluation of renal tumors is recommended in selected cases.