Serosal reaction in chronic gastric ulcers: an immunohistochemical and ultrastructural study.

AIM To study the serosal reaction in gastrectomy specimens with benign chronic peptic ulcers. METHODS Gastrectomy specimens were fixed in neutral buffered formalin and paraffin wax, and examined using immunohistochemical and ultrastructural techniques. RESULTS Nine of the 22 (41%) cases examined showed reactive hyperplasia of the serosal cells. The cells were predominantly spindle-shaped and were positive on staining with Cam 5.2, AE1/3 and for vimentin. Eight of nine were also positive for smooth muscle actin and five for desmin. Ultrastructural analysis of these cells suggests that they may be myofibroblastic in nature. CONCLUSIONS These results support the concept of "multipotential" subserosal cells which may differentiate into surface serosa or, in the reactive state, modulate the thin cytoskeletal filaments and become more myofibroblastic. Particular care should be taken not to confuse these reactive serosal cells with carcinoma or smooth muscle tumours in endoscopic biopsy specimens.