Fine needle aspiration for diagnosing a thymoma producing CA-125. A case report

This case report describes the cytologic appearance of a solid and cystic thymoma with high CA-125 content (35,532 microns/mL, measured by enzyme immunoassay) in the cyst fluid obtained by fine needle aspiration (FNA). The initial FNA yielded straw-colored fluid that contained scanty foam cells, lymphocytes and benign epithelial cells and was interpreted as a bronchial inflammatory cyst. The cyst fluid CA-125 was 35,532 microns/mL and serum CA-125, 5.2 microns/mL (normal < 15). In view of the discordance between the cytologic diagnosis, suspicious radiologic appearance and high fluid CA-125 level, FNA of the solid portion of the mass was performed. Smears/cell block examination showed large, cohesive clusters of benign, spindle-shaped epithelial cells (keratin positive) admixed with mature lymphocytes diagnostic of thymoma. This report illustrates the importance of (1) sampling solid areas of solid/cystic tumors, (2) rapid assessment of FNA material, and (3) appropriate clinical and radiologic correlation. It also describes the cytologic features of a solid/cystic thymoma with elevated CA-125 content in the cyst fluid.