Plexiform angiomyxoid myofibroblastic tumor of the stomach

Figure 1 Gross appearance of a case of plexiform angiomyxoid myofibroblastic tumor (PAMT). A: A reddish and lobulated tumor protrudes from the serosa; B: The cut section of the tumor. The tumor causes ulceration and perforation.

Figure 2 Histological appearance of PAMT. A: The tumor shows a multinodular plexiform growth pattern (HE stain, × 20); B: Spindle-shaped bland tumor cells are separated by an abundant intercellular myxoid matrix. The stroma is rich in small vessels (HE stain, × 100); C: Tumor cells possess oval nuclei and a slightly eosinophilic cytoplasm. The nucleoli are inconspicuous and the cell borders are indistinct (HE stain, × 200); D: The stroma is positive for Alcian blue stain (× 200); E: Stromal collagenization is occasionally observed (HE stain, × 200).

Figure 3 The results of immunohistochemical staining. A: The tumor cells are negative for KIT. The scattered KIT-positive cells are mast cells (× 200); B: The tumor cells are diffusely positive for smooth muscle actin (× 200).