Abstract
Objective : We analyzed typical features of cell clusters surrounding collagenous stroma (CS) in body fluid cytology and considered their significance in routine cytological diagnosis.
Study Design : Cytological specimens from 36 cases of malignant mesothelioma (MM) and 4,306 cases with reactive mesothelial cells (RM) were reviewed. CS was detected in 148 cases—23 of MM and 125 of RM. Cell clusters surrounding CS were divided into three structural patterns and cytochemistry, immunocytochemistry, and electron microscopy were conducted.
Results : TypeI clusters were seen in 118 cases (2.7%) of RM, but not in MM. They were often seen in the washing cytology (10.9%) but very rarely seen in the aspiration cytology (0.03%) (p<0.001). TypeII and III clusters were significantly frequently detected within MM cases—typeII, 23 cases, 63.9% ; typeIII, 7 cases, 19.4%—than RM—6 cases each, 0.14% (p<0.001). CS was invariably PS-positive, diastase-resistant, and metachromatic in Giemsa staining. In immunocitochemisty, some typeII CS showed positivity for laminin or typeIV collagen.
Conclusions : TypeI clusters were specific for RM and typically seen in peritoneal washing specimens. TypeII and III clusters were significantly seen in Mm cases. Some typeII CS contained basement membrane material, indicating that cytomorphological features of cell clusters surrounding CS may be of diagnostic use in evaluating the malignant potential of mesothelial cells.
