OBJECTIVETo explore cytological parameters that may identify the primary sites of metastatic adenocarcinomas in serous fluid.

METHODSSerous fluid specimens from 89 cases of metastatic adenocarcinomas (40 metastatic adenocarcinomas of lung, 6 metastatic adenocarcinomas of breast, 21 metastatic ovary adenocarcinomas, 22 metastatic gastrointestinal and pancreatic adenocarcinomas) were studied by using multiple morphologic parameters. Immunocytochemical S-P method was used to detect the expression of CA125, CA199, SPB and TTF-1 in 75 cases.

RESULTSMetastatic adenocarcinomas of different primary sites displayed certain different morphologic features, including the total amount of tumor cells, size of clusters, ratio of clusters over single cells, configuration of tumor clusters and the background of the smear. Cell clusters of small to medium sizes represented 95% and 100% in the metastatic adenocarcinomas of lung and breast, respectively. Most of the ovarian metastatic adenocarcinomas (85.7%) presented some large cell clusters and larger amount of cells, whereas certain metastatic gastrointestinal and pancreatic adenocarcinomas (45.5%) presented smaller number of cells and predominantly to be single cell in distribution (40.9%). Psammoma bodies were found in metastatic adenocarcinomas of lung and ovary. SPB and TTF-1 expression supported the diagnosis of adenocarcinoma of pulmonary origin. CA125 expression supported an ovarian origin. Although CA199 was seen in all groups of metastatic adenocarcinomas, nevertheless, its appearance in tumor cells in ascitic fluid specimens supported gastrointestinal and pancreatic origins.

CONCLUSIONMorpho-logic features of the cytological smear, immunohistochemical staining and clinical history are equally important in determining the primary sites of metastatic adenocarcinomas in serous fluid.