Presentation
History of dull upper abdominal pain for 2 years. No history of fever, vomiting, anorexia, or weight loss.
Patient Data
A well-defined mildly hypoechoic homogeneous ovoid-shaped mass lesion measuring 3.7 x 5.6 cm is seen in the right hypochondrium separate from the left lobe of the liver, pancreas, and gallbladder. No calcifications are seen in it. Some internal vascularity is seen in it on color Doppler ultrasound examination. Its exact nature as well as its origin is not clear and further evaluation with cross-sectional imaging is advised.
Findings: A well-defined mass measuring 4.9 x 5.8 cm is seen adjacent to the pyloric antrum. Multiple small hypodensities/cystic areas are seen in it. No calcifications or septations are seen in it. It shows moderate enhancement on post-contrast images. A well-defined hypodense lesion measuring approximately 11 x 15 mm is seen in the right hepatic lobe which is likely a hepatic cyst or hemangioma. A note is made of hypertrophy of the caudate lobe with normal hepatic veins and IVC. No significant abdominopelvic lymphadenopathy is seen.
Conclusion: Well-defined enhancing soft tissue mass adjacent to the pylorus, which is likely a gastric stromal tumor (GIST); other possible differential diagnosis includes leiomyoma, and neurofibroma.
Case Discussion
After the imaging work-up, the patient underwent ultrasound guided Tru-Cut biopsy, followed by the complete excision of the mass laparoscopically.
Histopathological diagnosis: Epithelioid gastrointestinal stromal tumor (GIST) low grade, encased by a thin layer of serosa. Tumor size 5 x 4 x 4 cm. Mitotic count 0/150 HPF. Proliferation index approximately 5%. Negative for tumor necrosis.
Immunohistochemistry: The tumor cells show a uniform positivity for vimentin and CD117. S100 also shows a uniform but weaker positivity limited to cytoplasm. CK AE1/3, CD34, SMA and desmin show a negative reaction. Ki-67 stains about 5% of the tumor cells. A single layer of flattened mesothelial cells is highlighted by CK AE1/3 and HBME-1. Large spaces with albuminous fluid show no endothelial lining.
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