Inflammatory myofibroblastic tumor of the gallbladder: a case report and literature review.

A 50-year-old man had undergone chemotherapy and radiotherapy for malignant lymphoma 1 year earlier. Follow-up computed tomography revealed a gallbladder polyp. Transabdominal ultrasound demonstrated a 20-mm hypoechoic sessile polyp with basal waist in the gallbladder fundus; the surface was covered with a hyperechoic layer of non-uniform thickness. On contrast-enhanced computed tomography, the polyp showed an early uniform and sustained staining pattern. Magnetic resonance imaging revealed that the polyp had low and slightly high signal intensities on T1- and T2-weighted imaging, respectively. Gallbladder bed resection was performed with the diagnosis of special tumor. Histologically, the polyp comprised a proliferation of myofibroblast-like spindle cells with inflammatory cell infiltration, without muscularis propria or vascular invasion. Most of the polyp surface was covered with necrotic exudate, and part of the normal epithelium remained. Consequently, a diagnosis of inflammatory myofibroblastic tumor was made. The sessile shape with basal waist, epithelium shedding, and surface necrotic exudative matter may represent intraluminal expansive growth such as a subepithelial tumor. A surface with a hyperechoic layer of non-uniform thickness on gallbladder polyp can help in the diagnosis of a tumor with expansive growth directly under the epithelium with stretching/rupture of the epithelium.