Plexiform angiomyxoid myofibroblastic tumor (PAMT) of the stomach. A case report focusing on its characteristic growth pattern

Abstract

Plexiform angiomyxoid myofibroblastic tumor (PAMT) is a rare mesenchymal tumor of the stomach. We report herein a case with CT findings, which illustrate the characteristic growth pattern of PAMT. A 27-year-old female patient visited our hospital because of epigastric pain and anemia. The CT scan showed a heterogeneous tumor in the gastric antrum, which was drastically enhanced with contrast medium, and consisted of a number of highly stained small nodules around the tumor rim. The resected tumor, 4.6 cm in size, was c-kit negative and SMA-positive by immunohistochemistry, and composed of bland spindle cells which were separated by abundant myxomatous stroma. The tumor showed plexiform growth in the entire stomach wall, with multiple nodules protruding outward within the serosa. The CT findings in this case reflect the characteristic PAMT growth pattern, and are distinct enough to differentiate it from gastrointestinal stromal tumor (GIST).

Keywords: CT; GIST; PAMT; diagnosis.

Figure 1

CT scan of the tumor. A. Unenhanced CT image shows inhomogeneous tumor mass in the lower body of the stomach. B. Contrast-enhanced CT image revealed a tumor mass with an inhomogeneous, prominent enhancement in the late phase of contrast imaging.

Figure 2

Laparotomy finding at the surgery.

Figure 3

Gross appearance of the tumor. A. A submucosal tumor with focal ulceration is observed. Bar: 5 mm. B. The cut section of the tumor. Lobulated tumor is found in all layers of the gastric wall.

Figure 4

Histological appearance of the tumor. A. The tumor shows a multinodular plexiform growth pattern. B. Fibromyxoid nodules of tumor extend into serosal surface. C. The tumor contains spindle-shaped bland tumor cells in a fibromyxoid stroma, which is rich in small caliber blood vessels. D. Although the tumor disrupted the vessel wall, there was no evidence of invasion of the intravascular lumen.