Renal chromophobe cell carcinoma: limitations of paraffin-embedded tissue

Chromophobe cell carcinoma of the kidney is distinguished from other renal cortical tumors by the ultrastructural presence of numerous cytoplasmic vesicles of unknown composition. Failure to detect vesicles in paraffin-embedded tissue in the archival material of 10 putative chromophobe cell tumors stimulated an investigation into the effects of fixatives and dehydrating solvents on vesicle integrity. We found that although vesicles are removed by dehydrating agents during paraffin embedding, osmium tetroxide postfixation prevents vesicle loss during dehydration for electron microscopy. We conclude that paraffin-embedded tissue is useless for histochemical studies of vesicle composition and cannot be employed for the ultrastructural confirmation of a histologic diagnosis of chromophobe cell carcinoma since the intracellular vesicles are no longer present.