Caveolin-1 (CAV-1) is a cell membrane-associated structural component of flask-shaped plasma membrane invaginations termed caveolae. CAV-1 is expressed at different levels in different tissues, with the highest in adipocytes, endothelial cells, fibroblasts, and mesothelial cells. Anti-CAV-1 is useful in assisting in the identification of epithelioid mesothelioma. A study by Amatya et al. indicates CAV-1 expression in all 80 (100%) epithelioid mesotheliomas, whereas only 6/80 (7.5%) of the lung adenocarcinomas were positive for CAV-1. Staining in most mesotheliomas was strong and diffuse when compared with the weak, focal staining (no more than 1% of the tumor cells) seen in the lung adenocarcinomas, anti-CAV-1 is considered a very useful marker for assisting in discriminating between these two malignancies. They also indicated that anti-CAV-1 is comparable to other mesothelioma markers such as anti-calretinin and anti-D2-40 (podoplanin) that are commonly used to assist in the differentiation between epithelioid mesotheliomas and lung adenocarcinomas. Anti-CAV-1 is also useful in identification of Ewing sarcoma/PNET. Literature indicates CAV-1 expression in 368 (96%) of 383 cases of Ewing sarcoma/PNET. In summary, anti-CAV-1 is very useful in the differentiation of epithelioid mesothelioma from lung adenocarcinoma and identification of Ewing sarcoma/PNET.