Commonest histological type of carcinoma testis is -
Tumors of the testis are a heterogeneous group of neoplasms that include germ cell tumors and sex cord stromal tumors. 
In postpubertal males, 95% of testicular tumors arise from germ cells, and all are malignant
Teratoma
Yolk sac tumor
Seminoma
Choriocarcinoma