CTLA4 and thymoma: In addition, atypical histological type thymoma (OS = 65.73 months) (Figure 5B) showed a significant (p = 0.0055) reduced survival respect to typical thymoma (OS = 188.22 months) confirming that high CTLA-4 expression in atypical thymoma (Figure 1D) is associated with negative prognosis.