Putative Malignant Pleural Mesothelioma in situ (MPMIS) with Sequential Acquisition of Genomic Alterations on Fluorescence in situ Hybridization (FISH) Examination.

Malignant pleural mesothelioma (MPM) is a rare and deadly disease. A precursor in situ lesion, malignant pleural mesothelioma in situ (MPMIS), has recently been proposed. On cytological examination, the distinction between reactive and malignant mesothelial cells is often challenging, and sometimes even impossible without ancillary methods.

Extensive Emperipolesis of Neoplastic Lymphocytes by Mesothelial Cells in Pleural Effusion Cytology in a Case of a Mediastinal T-Cell Lymphoblastic Lymphoma: A Rare but Diagnostically Useful Phenomenon.

Emperipolesis is a biological process defined by the presence of an intact cell within the cytoplasm of another cell. In pleural fluid cytology, the phenomenon is very rare but has already been described in B-cell lymphoma. Here, we report the first case of a T-cell lymphoma diagnosed on a pleural fluid exhibiting extensive emperipolesis of tumor cells by mesothelial cells.

Detection of ROS1-positive non-small cell lung cancer on cytological specimens using immunocytochemistry.

Background: Rearrangements of the ROS1 oncogene are found in 1% to 2% of non-small cell lung cancers (NSCLC) and are regarded as mutually exclusive oncogenic driver mutations. Since the approval of targeted therapy for ROS1-positive NSCLC, ROS1 testing has become a part of the diagnostic routine. Fluorescence in situ hybridization (FISH), optionally selected for by immunohistochemistry on histological material, is a common practice for the detection of ROS1 rearrangements.