An EMA negative, desmin positive malignant mesothelioma: limitations of immunohistochemistry?

Histopathologists in the current environment of medical negligence and litigation are more likely to use immunohistochemical investigations in their day-to-day practice to support their diagnosis and avoid future litigation. The caveat is that relying on immunohistochemistry is a double-edged sword and pathologists should be familiar with its limitations. We present a case of primary malignant peritoneal mesothelioma with an unusual immunohistochemical profile—desmin positive, EMA negative—and wish to highlight the importance of cautiously interpreting immunohistochemistry profiles when they do not fit the clinical history and histological appearance.