Plexiform angiomyxoid myofibroblastic tumour: differential diagnosis of gastrointestinal stromal tumour in the stomach.

Mesenchymal tumours other than gastrointestinal stromal tumours are rare in the stomach. Nevertheless it is important to incorporate them into the differential diagnosis. Plexiform angiomyxoid myofibroblastic tumour is a recently described new entity of a presumably benign mesenchymal gastric tumour. This report presents what is believed to be the third case of this tumour. The tumour is characterised by bland spindle cells in a plexiform pattern, a mucinous extracellular matrix and a network of thin blood vessels. These findings are completely in line with the two previous reported cases. There was a strong positivity for alpha-smooth muscle actin and a low proliferation index (<2%). The tumour had no C-KIT or CD34 expression and no mutation in the C-KIT and PDFGRalpha genes. Plexiform angiomyxoid myofibroblastic tumour may present a new mesenchymal tumour entity in the stomach.