Role of Immunocytochemistry in the Cytological Diagnosis of Mesothelioma.

Background: Mesothelioma is an aggressive malignancy of the serosal surfaces with very poor prognosis. It traditionally manifests in older patients and at an advanced stage which results in minimal improvement in prognosis despite the recent advances in management. Early detection would therefore significantly impact management and potentially improve survival. Mesothelioma frequently presents with recurrent effusions, posing cytology as the initial procedure in the workup. A definitive diagnosis would not only spare the patients additional diagnostic procedures but also potentially afford them an opportunity for early surgical intervention and therapy.

Summary: In this article, we review the role of immunocytochemistry (ICC) in the workup of mesothelioma. The various ICC markers to confirm or rule out mesothelial lineage are reviewed. In addition, newly introduced molecular surrogates that confirm the malignant nature of the mesothelial cells and support a definitive diagnosis of mesothelioma are discussed. We also briefly discuss the theranostic implications of such markers and potential impact of such recent advances on the cytological diagnosis and reporting of mesothelioma.

Key messages: The cytological diagnosis of mesothelioma no longer requires the extensive expertise in morphological analysis and can be offered based on supporting ICC that confirms the mesothelial lineage and malignant nature of the cells.