Computed tomography of anterior mediastinal tumors. Differentiation between thymoma and germ cell tumor.

Computed tomographic (CT) features in 10 patients with germ cell tumor of the mediastinum and 15 with thymoma were compared with surgically resected specimens. The CT findings of the internal structure of tumors were the most important factor for specific diagnosis. Germ cell tumors showed a round mass without distinct lobulation, frequently with calcification appearing as a globular shape, and especially in benign tumors as an arched shape along the wall. Homogeneous low density masses (near-water) with a thick wall were benign and non-homogeneous density masses (a mixture of near-water and soft tissue) were malignant. Thymoma usually showed a solid mass with lobulation and sometimes had an eggshell type of calcification in the tumor. Therefore, CT is of importance in the diagnosis of anterior mediastinal masses.