An Unusual Cause of Recurrent Subepithelial Mass in the Stomach

Abstract

Question: A 58-year-old woman presented with a subepithelial tumor, approximately 2 cm in size, incidentally detected in the posterior wall of upper body of the stomach during a screening endoscopy (Figure A). The sample from an endoscopic ultrasound-guided fine-needle biopsy revealed spindle-shaped cells arranged in a fascicular pattern. The spindle cells were immunopositive for c-Kit, cluster of differentiation 34, DOG-1, and smooth muscle actin. The patient was diagnosed with a gastrointestinal stromal tumor (GIST) and underwent laparoscopic wedge resection. The tumor was completely resected with clear margins. The maximal tumor size was 2.3 cm, and the mitotic count was 2 per 50 high-power fields; therefore, it was diagnosed as a GIST with a low risk of malignant potential. Follow-up abdominal computed tomography after 2 years showed a new low-density mass in the previous resection site (Figure B, arrow). Endoscopy showed no definite lesion at the resection site (Figure C), and endoscopic ultrasound revealed a 1.5-cm heterogeneous hypoechoic lesion originating from the muscularis propria (Figure D). Laparoscopic wedge resection was performed again for a definitive diagnosis and treatment. What is your diagnosis? See the Gastroenterology web site (www.gastrojournal.org) for more information on submitting your favorite image to Clinical Challenges and Images in GI. Histopathologic examination of the resected specimen revealed sweeping fascicles of bland and uniform spindle cells with collagenous stroma and compressed, thin-walled vessels (Figure E). The spindle cells were immunonegative for c-Kit (Figure F), cluster of differentiation 34 (Figure G), DOG-1 (Figure H), and S-100 protein, and were immunopositive for smooth muscle actin (Figure I), which suggested the exclusion of GIST. Therefore, additional immunohistochemistry was performed for the differential diagnosis. The tumor cells were negative for anaplastic lymphoma kinase but positive for nuclear β-catenin (Figure J). Based on morphologic and immunohistochemical findings, a diagnosis of a desmoid tumor occurring at the previous resection site of the gastric GIST was made. No further treatment was provided because the tumor was completely resected. No signs of recurrence or metastasis were found during 12 months of follow-up. Desmoid tumors are rare mesenchymal tumors occurring in patients with risk factors, such as a previous history of abdominal surgery, familial adenomatous polyposis, or pregnancy, and they can be easily mistaken for GIST because both tumors show similar clinical presentation and morphology.1Murshid A.A. Al-Maghraby H.Q. Subsequent development of desmoid tumor after a resected gastrointestinal stromal tumor.Case Rep Pathol. 2018; 2018: 1082956Google Scholar The desmoid tumor and GIST are both microscopically characterized by spindle-cell proliferation, and the differential diagnosis of these two tumors is performed mainly by immunohistochemistry. Because desmoid tumors usually have activating mutations in β-catenin, abnormal nuclear positivity of β-catenin is seen in most desmoid tumors.2Lu Q. Wang K. Liu D. et al.Stomach desmoid tumor: a case report and review of the literature.Int J Clin Exp Pathol. 2017; 10: 10531-10538Google Scholar Surgical resection with a negative margin is currently the treatment of choice. When local recurrence occurs or complete surgical resection is not feasible, radiotherapy, chemotherapy, and other comprehensive therapies, such as estrogen receptor antagonists and nonsteroidal anti-inflammatory drugs, should be provided.2Lu Q. Wang K. Liu D. et al.Stomach desmoid tumor: a case report and review of the literature.Int J Clin Exp Pathol. 2017; 10: 10531-10538Google Scholar Owing to the rarity of gastric desmoid tumors, information about their prognosis is very limited. According to a review of the literature on gastric desmoid tumors, no recurrence was reported during follow-up assessments,2Lu Q. Wang K. Liu D. et al.Stomach desmoid tumor: a case report and review of the literature.Int J Clin Exp Pathol. 2017; 10: 10531-10538Google Scholar indicating a good prognosis. However, considering the local recurrence rate of 13% for intra-abdominal sporadic desmoid tumors,3Wilkinson M.J. Fitzgerald J.E. Thomas J.M. et al.Surgical resection for nonfamilial adenomatous polyposis-related intraabdominal fibromatosis.Br J Surg. 2012; 99: 706-713Google Scholar regular follow-up is mandatory.