Presence of smooth muscle cell differentiation in plexiform angiomyxoid myofibroblastic tumor of the stomach: a case report

Abstract

Plexiform angiomyxoid myofibroblastic tumor (PAMT) is a recently described distinctive gastric mesenchymal entity with a peculiar plexiform pattern, bland spindle cells and a myxoid stroma rich in arborizing blood vessels. In this study, we report a new case of this rare gastric tumor with a subset of tumor cells derived from smooth muscle differentiation. A 32-year-old Chinese man was admitted with a gastric mass. He did not experience any discomfort, and gastroscopy showed an elevated mass in the anterior wall of the gastric antrum. Endoscopic ultrasound examination revealed a focal hypoechoic lesion protruding into the lumen. A partial gastrectomy was performed, and the patient made an uneventful recovery and remains well 3 years later. The tumor in this case depicted all the typical histopathologic and immunochemical features of gastric PAMT, except that a small subset of tumor cells was partially immunoreactive for desmin and H-caldesmon. Based on the findings of this case, we think that PAMT may contain tumor cells derived from smooth muscle differentiation, and therefore this tumor may be more than just purely myofibroblastic in nature.

Keywords: Plexiform angiomyxoid myofibroblastic tumor; gastric mesenchymal tumor; myofibroblast; plexiform fibromyxoma; stomach.

Figure 1

Gastroscopy image of PAMT in the stomach. An elevated mass can be seen in the anterior wall of the gastric antrum.

Figure 2

Microscopic findings for the PAMT. (A) A plexiform growth pattern is observed, with spindle tumor cells separated by an abundant intercellular myxoid stroma. (B) The abundant stroma stained positive with Alcian blue. (C) The tumor cells were positive for H-caldesmon and (D) desmin.