They are particularly common in the colon. They sometimes become malignant so that microscopic examination is important. The term adenoma is also used since they are tumors of glandular origin.
Leiomyomas are benign tumors composed of smooth muscle frequently found in the stomach and uterus.
In the stomach they usually remain small and of no clinical importance, but in this case the tumor has reached the size of a lemon. The overlying mucosa has been stretched so that focal ischemic necrosis has occurred with ulceration and erosion of underlying blood vessels.