FPGS and thymic carcinoma: Studies have shown that the increased expression of tumor-associated genes, such as FPGS (folylpolyglutamate synthase)/GGH (gamma-glutamyl hydrolase) and VEGF (vascular endothelial growth factor), are related to the degree of malignancy in thymic carcinoma and B3 thymoma.11, 15 Studies have also shown that c-kit expression is significantly lower in thymic adenoma compared to thymic carcinoma; C-kit expression was detectable in approximately 70–86% of patients with thymic carcinoma, compared to only 0–5% of thymic adenomas.