Endoscopic freehand full-thickness resection of a gastric leiomyosarcoma initially diagnosed as gastric leiomyoma on endoscopic ultrasound-guided fine-needle biopsy.

BACKGROUND AND AIMS: Gastric leiomyosarcoma is a rare tumor arising from the smooth muscle of the stomach that is genetically distinct from gastrointestinal stromal tumors. To date, there are only 24 documented cases of confirmed gastric leiomyosarcoma, to our knowledge. We present the case of a gastric mass initially diagnosed as gastric leiomyoma based on endoscopic ultrasound-guided fine-needle biopsy histopathology, later reclassified as a primary gastric leiomyosarcoma after endoscopic full-thickness resection.

METHODS: The lesion was too large to fit into a resection cup and could not be resected using an Ovesco full-thickness resection device system (Ovesco Endoscopy AG, Tübingen, Germany). Resection was subsequently completed with an endoscopic freehand full-thickness resection.

RESULTS: The patient was referred to a specialized sarcoma unit, where he underwent laparoscopic gastric fundal resection with clear margins. After complete surgical excision, the patient recovered well, and no additional surgery or adjuvant systemic therapy was required.

CONCLUSIONS: Gastric leiomyosarcoma may arise from leiomyoma de novo, or through malignant transformation. This case demonstrates that it is important to consider full resection of atypical appearing, large, or enlarging gastric leiomyomas due to the risk of underlying leiomyosarcoma. A leiomyosarcoma can be misdiagnosed as a leiomyoma if the biopsy needle, angled improperly, only samples superficial tissue, and the malignant tissue may reside in deeper layers.