B7-H1-positive malignant mesothelioma, sarcomatoid type: Neoplastic spindle cells are growing in a haphazard and tumefactive pattern (A, A insert). The neoplastic cells show diffuse and strong membranous and cytoplasmic expression of B7-H1 (B, B insert). B7-H1-positive malignant mesothelioma, epithelioid type: Neoplastic epithelioid cells are invading into adipose tissue (C, C insert). The neoplastic cells are strongly and diffusely positive for B7-H1 with a predominant cytoplasmic and focal membranous staining pattern (D, D insert). B7-H1-negative malignant mesothelioma, biphasic type: Neoplastic spindle cells are growing in a tumefactive pattern. Islands of neoplastic epithelioid cells are also present (E, E insert). The neoplastic cells are negative for B7-H1 (F, F insert). Magnification × 100 (A-F), × 400 (A-F-inserts).