Abstract
Back ground : Ascites cytology occasionally involves, malignant cell clusters with collagenous stroma (CS), but nonneoplastic cell clusters with CS are rare. We report a case involving numerous reactive mesothelial cell clusters with CS.
Case : A 46-year-old woman admitted for resection of a liver tumor histologically diagnosed as neuroendocrine carcinoma experienced tumor recurrence with peritoneal dissemination and abundant ascites 4months postoperatively despite anticancer therapy.
Cytological examination of ascites showed numerous intermediate or small cell clusters, most with CS at the center. Cells were round to cuboid with clear cytoplasm and round to oval nuclei with fine granular chromatin and immunopositive for calretinin, D2-40, WT-1, and podoplanin, but not for synaptophysin or EMA—findings corresponding to those of reactive mesothelial cells, but not of cancer cells. CS was positive for type IV collagen at the periphery.
Conclusions : Our case, showing numerous reactive mesothelial cell clusters with CS, should alert pathologists and cytotechnicians to the unusual nature of such an case.
