S3189 Not Just a GIST: A Rare Case of Gastric Leiomyosarcoma

Abstract

Introduction: Leiomyosarcoma (LMS) is a malignant neoplasm showing smooth muscle differentiation. Before the recognition of gastrointestinal stromal tumors (GISTs), leiomyoarcomas were commonly reported in the gastrointestinal tract due to misclassification. Now, these tumors are considered rare with only 16 cases of gastric LMS reported in the post-GIST era. We present the 17th case of primary gastric LMS. Case Description/Methods: An 81F with a history of GERD,CHF and Afib presented for evaluation of syncope. She had also suffered with increased fatigue, poor appetite, 30lb unintentional weight loss, and a “gnawing” post-prandial epigastric pain. Her last EGD was 4 years prior which showed non bleeding erosive gastropathy and a non obstructing Schatzki’s ring. Biopsies showed chronic gastritis without evidence of dysplasia or H. Pylori. On admission, pertinent labs included Hg of 11.5 g/dL, MCV 99.7 fL, WBC 11.02 k/uL, and albumin 2.8 g/dL. She underwent an EGD which showed a large, infiltrative, transmural, ulcerated, non-circumferential mass in the greater curvature of the stomach. EUS showed a hypoechoic lesion which appeared to extend to the cardia by extrinsic involvement of the gastric wall. Biopsies showed an ulcerated spindle cell neoplasm which stained negative for C-kit and DOG1, but were strongly positive for desmin. This conformed the diagnosis of gastric leiomyosarcoma. Discussion: Before the development of immunohistochemical staining for C-kit, many GISTs were misdiagnosed as LMSs and leiomyoblastomas. Now these tumors are considered rare with only 16 prior case reports. The diagnosis mainly relies on pathologic examination with SMA, desmin, and h-caldesmon are positive in the majority ( >70%) of LMSs. CD117 (KIT), DOG 1 and CD34 are negative. It is important to rule out Carney tried, which is a type of multiple endocrine neoplasia which encompasses LMSs, pulmonary chondroma, and extra-adrenal paragangliomas. Complete for LMS surgical resection with negative margins remains the gold standard of treatment. It is important to note that not every spindled lesion is a GIST, as diagnosis will change management. As opposed to GISTs, LMSs are not likely to respond to Imatinib. Due to concern for splenic invasion, neoadjuvant chemotherapy was pursued in our patient with Ifosfamide and doxorubicin prior to surgical resection. Due to her other comorbidities, she was felt to be too high risk for surgery and she eventually chose to pursue hospice.Figure 1.: Figure 1 1a: Ulcer in the incisura of the stomach 1b: Ulcer status post hemostatic clip and argon plasma coagulation (APC).