Gastrointestinal stromal tumor presenting with prominent calcification

Abstract

We present a rare case of a gastrointestinal stromal tumor (GIST) in the stomach with prominent calcification at presentation. A 61-year-old woman visited our hospital because of epigastric discomfort. A spherical calcified lesion with a diameter of about 30 mm was incidentally shown in the left upper quadrant on an abdominal X-ray. Computed tomography demonstrated that the tumor was growing from the upper gastric body, with calcification in the peripheral ring area. A laparoscopic partial gastrectomy was performed, and the resected specimen revealed a well-circumscribed tumor with exophytic growth from the gastric muscularis propria. Microscopic examination revealed spindle-shaped tumor cells with calcification and hemorrhage. Additionally, positive immunoreactivity of the tumor to KIT and CD34 and a low mitotic index resulted in the diagnosis of very low risk GIST. There are a few case reports of heavily calcified GIST, although solitary or punctate calcification of primary GIST has been reported in several case series. Dystrophic calcification of necrotic or degenerative tissue is the supposed cause of primary calcified GISTs. In contrast, appearance of calcification after administration of imatinib mesylate, which may be one indicator of disease response, is possibly caused by a different mechanism.

Keywords: Calcification; Computed tomography; Gastrointestinal stromal tumor; Imatinib mesylate; Stomach.

Figure 1

Radiological findings. A: Abdominal X-ray indicated a spherical calcified lesion in the left upper quadrant; B: Barium study showed a round calcification bordering the gastric wall.

Figure 2

Computed tomography and magnetic resonance imaging findings. Contrast-enhanced axial (A) and coronal (B) computed tomography examination demonstrated that the marginal zone of the tumor was calcified, and that the internal portion of the tumor was enhanced heterogeneously. Magnetic resonance imaging T1-weighted image (C) and T2-weighted image (D) revealed a low intensity marginal zone of tumor reflecting calcification.

Figure 3

Endoscopy and endoscopic ultrasound of stomach. A: Endoscopic examination revealed a round submucosal tumor; B: The tumor originated from the fourth layer of the gastric wall as indicated by endoscopic ultrasound. The deeper section could not be visualized because of calcification.

Figure 4

Pathological findings. A: Sliced sections of the resected mass demonstrated a firm, solid, whitish-gray parenchyma with circular calcification and internal bleeding; B: Microscopically, the tumor was characterized by spindle-shaped tumor cells (hematoxylin and eosin, original magnification ×100); Immunohistochemically, the tumor cells were positive for KIT (C) and CD34 (D).