Background: Mesothelial proliferations range from reactive lesions to benign and malignant tumors, bearing witness to the plasticity of these cells. Their diagnosis often requires combination of morphological assessment, immunohistochemistry, and molecular testing.
Summary: Considerable progress has been made in recent years in all the above aspects. The separation of reactive from neoplastic mesothelial proliferations has become more robust. Mesothelioma in situ is now recognized as precursor of invasive mesothelioma and better tools exist for its differentiation from benign mimics. Differentiating mesothelial tumors from other malignancies, including metastatic carcinomas, sarcomas, and other tumors, is now more easily achieved. Genetic conditions which predispose to development of mesothelioma at a young age have been identified and characterized. These issues are discussed in this review.
Key messages: Mesothelial pathology is an evolving field and more knowledge of these processes is likely to be gained in coming years. The diagnosis of these tumors requires experts with subspecialty in cytology, thoracic, soft tissue/bone, and gynecologic pathology, cooperating with surgeons, radiologists, and oncologists at specialized centers.
Keywords: Ancillary testing; Biopsy; Effusion; Malignant transformation; Mesothelium; Plasticity.
© 2026 The Author(s). Published by S. Karger AG, Basel.