FLUID CYTOLOGY UPDATE: THE MANY FACES OF MESOTHELIAL CELLS AND MALIGNANT CELLS IN FLUID CYTOLOGY, DIAGNOSTIC PITFALLS AND ANCILLARY STUDIES
Authors: Khalbuss E. W. 
Published: August 2006

Fluid cytology has a clinical significance in the management of patients with malignancy. Effusions are often the first clinical symptom of malignant tumors or of their metastatic manifestation. In known malignancies effusins are an omnious sign. In one third of malignant effusions, cytology gives the first indication of malignancy. Therefore, cytological diagnoses of effusions are of great clinical importance. Microscopic evaluation of body fluid cytology is not always straightforward. The two lectures and the afternoon workshop session review the literature, describe the cytomorphological criteria in the diagnosis of reactive/proliferative mesothelial cells, inflammatory/ infectious conditions and neoplastic lesions in body fluid with emphasis on the many faces and similarities of reactive mesothelial cells and malignant cells. The lectures will review several interesting cases in fluid cytology with emphasis on problematic areas in body cavity luid cytology. The cytological criteria of benign conditions and malignant neoplasms in fluid cytology preparations are different from those in fine needle aspiration specimens procured from the same lesions. For example, monolayered sheets as commonly seen in fine needle aspiration smears from adenocarcinomas are not present in effusion preparation. Small cell undifferentiated carcinomas in effusion may show proliferative spheres of tumour cells that wrap around one another with an onionskin appearance. Lymphomas in effusion may show marked apoptosis or vacuolization. One of the great challenges in the cytological diagnosis of effusions is the distinction between reactive mesothelial cells/histiocytes and malignant cells. Furthermore, numerous diagnostic pitfalls of fluid cytology may be encountered such as mesothelial cell hyperplasia, collagen balls, endometriosis, endosalpingiosis; psammoma bodies, pseudoeosinophilia, fluid eosinophilia, rheumatoid arthritis effusion, lupus pleuritis, effusins with small cells, malignant effusion with single cell population; mucinous and serous tumours in female patients, cancer treatment effects, liver cirrhosis effusion, renal failure effusions, and pancreatitis effusins. Preparation of cell blocks and ancillary studies are of value in the work‐up and management of patients who present with cytologic mimickers of malignancy on fluid cytology. The first lecture will start with an instructor‐audience interactive discussion on the cytomorphological criteria in the diagnosis of reactive/proliferative mesothelial cells, inflammatory/ infectious conditions and neoplastic lesions in body fluid. The second lecture will address the diagnostic pitfalls of papillary structures, vacuolation of mesothelial cells, psammoma bodies, collagen balls, endometriosis, endosalpingiosis, and the borderline tumours reporting. The second lecture will also address the role of ancillary studies such as special stains, immunocytochemical staining, flow cytometric studies and EM in body fluid cytological examination.References:  1. Motherby H, Nadjari B, Friegel P, Kohaus J, Ramp U, Bocking A. Diagnostic accuracy of effusion cytology. Diagn Cytopathol. 1999; 20(6): 350–72. Das DK. Serous effusions in malignant lymphomas: A review. Diagn. Cytopathol. 2006; 34: 335–347.3. Selvaggi SM Diagnostic pitfalls of peritoneal washing cytology and the role of cell blocks in their diagnosis. Diagn Cytopathol. 2003; 28(6): 335–41.