EFFUSIONAL CYTOLOGY OF WELL-DIFFERENTIATED PAPILLARY MESOTHELIOMA: A SERIES OF 7 CASES

Well-differentiated papillary mesothelioma (WDPM) in an un common subtype of mesothelioma that usually follows an indolent clinical course. Most cases have been described in the tunica vaginalis, or in the peritoneum of woman without a history of asbestos exposure; WDPM con occu also in the pleural cavity, in association with asbestos exposure in 50% ofa cases (Am J Surg Pathol 2001;25:1304-9). Although WDPM present with recurrent effusions, most reports in the literature have focused an histology (superficial spreading of papillary structures without/with limited invasion, and no mitosis) and less on cytology. The present study of 7 cases of WDPM located in the peritoneal (n=4), pleural (n=2), and pericardial (n=1) cavities, comprises the experience of a single institution in Rome, Italy, with respect to cytology, prognosis and status of asbestos exposure. The patients were 3 males (age range 50-64 years) and 4 females (69-87 years). In 2 men, a possible history of asbestos exposure was identified in the construction work. All cases had recurrent effusions. In 4 cases, there was a histological validation of the cytological diagnosis. Immunohistochemistry was done in all cases. Cytology of effusions showed papillary and tubular structures with minimal atypical features such as small nucleoli and nuclear overlapping. There were also large single cells, often bi- or multinucleated. Mitosis and apoptosis were seen only in one case. Macrophages and lymphocytes were seen in the background. Prolonged survival was ob-served in 4 patients for whom a follow-up was available (up to 11 years). Alive patients have a stable disease requiring multiple effusion drainage. Cytologists should be aware of WDPM, which is a clinco-pathologic entity distinct from conventional diffuse malignant mesothelioma and hyperplasstic precesses.