Abstract
Coelom cavities (pleura, pericardium, peritoneum, tunica vaginalis testis) lined with mesothelial lining derived from the mesoderm, represent a frequent place of propagation of pathological processes both from the neighbourhood and primary. These are most often manifested by effusion, whose cytological examination contributes significantly to the diagnosis.
Each larger amount of fluid in the coelom spaces is pathological. The primary task is, as a rule, the identification of tumour cells, more often of metastatic origin (with decreasing frequency (adenocarcinomas, melanoma, sarcomas) than primary (mesothelioma, primary lymphomas of coelom cavities).
The differentiation of carcinoma or other tumour populations from mesothelial cells often requires, following careful morphological evaluation, the indication of complementary methods of staining, immunocytochemistry (in haematological malignancies, preferably in combination with flow cytometry) or methods of molecular pathology. Standardization is not yet advanced in this diagnostic area, however there is a consensus for a panel to distinguish between carcinoma and mesothelioma.
Diagnosis is always generated via a summation of features. A good outcome requires adequate control of all three phases of the diagnostic process and a clear and unambiguous diagnosis, or differential diagnosis, formulation.