Cytoplasmic microvesicles in chromophobe cell renal carcinoma demonstrated by freeze fracture.

In the chromophobe cell type of renal carcinoma, cytoplasmic microvesicles (frequently with "inner vesicles") demonstrable by transmission electron microscopy are one of the most important diagnostic features. The present paper reports on these microvesicles in freeze fracture replicas. Their diameter is mainly between 140 and 300 micron, but smaller and very much larger vesicles may also occur. The vesicle membrane is devoid of, or contains only scanty intramembranous particles. Cytoplasmic invaginations, probably the precursors of "inner vesicles" can also be detected. Connections with the agranular endoplasmic reticulum, mitochondria or other cell components could not be documented. Larger vacuoles limited by a membrane and containing large numbers of microvesicles have been interpreted as autophagic vacuoles. In freeze fracture replicas, there are marked differences between the chromophobe cell and the clear cell type of renal carcinoma, providing further evidence that the chromophobe cell type is a distinct entity.