Comparative light and electron microscopic observations of the cytoplasmic matrix in renal carcinomas.

Abstract

With the aim of elucidating the structure and composition of the cytoplasmic matrix in renal carcinomas, eleven tumors obtained during surgery were subjected to a comparative light and electron microscopic study, complemented with determinations of glycogen in homogenates of tumor tissue and normal renal cortex. The findings indicated that in carcinomas of clear cell type, translucency of cytoplasm is due to the presence of glycogen, in some instances in combination with occurrence of neutral fat. These substances occupy the major part of the cytoplasm while cytoplasmic organelles are sparse. The granular cells contain abundant mitochondria while glycogen and fat is lacking or is only present in small amounts. PAS-positive, non-glycogenic material could not be demonstrated within the cytoplasm of either cell type; such material is, however, forming extracellular “coatings” on both cell types and is probably of glycoprotein nature. The significance of the findings was discussed and reference was made to pitfalls in the technique for properly demonstrating different types of PAS-positive materials. A comparison with the appearance of routinely fixed tissues indicated that reliable information concerning PAS-positive substances cannot be obtained from such material.