Cytologic appearances of pheochromocytoma and medullary thyroid carcinoma occurring within a family.

The cytologic and histochemical characteristics of the tumor cells from medullary thyroid carcinoma and pheochromocytoma are described. In cell samples obtained from medullary thyroid carcinomas, amyloid deposits were detected both intracellularly and extracellularly. Medullary thyroid carcinoma cells, as well as pheochromocytoma cells, showed positive for both argentaffin and argyrophil reactions. The diagnostic significance of intracellular amyloid deposits and of positive silver and chromaffin reactions of the intracytoplasmic granules may be stressed in establishing the cytologic diagnosis of medullary thyroid carcinoma and/or pheochromocytoma.