Endometriosis of the rectosigmoid colon mimicking gastrointestinal stromal tumor

Endometriosis is defined as the growth of functional endometriotic gland and stroma outside the uterine cavity. Although it is common in women of reproductive age, extragenital endometriosis is considerably rare. Due to its frequent localization at the rectosigmoid junction in the gastrointestinal system, endometriosis may manifest with abdominal pain, constipation, and rectal bleeding. Gastrointestinal stromal tumor is the most common mesenchymal tumor of the gastrointestinal system and develops from the muscularis propria. Its extraluminal component is prominent. This study aimed to report a rare case of a 37-year-old patient who was operated with laparoscopic colon resection for a malignant-appearing submucosal mass with indistinct borders at the rectosigmoid junction that received the final diagnosis in histopathological examination. Endometriosis should be considered in the differential diagnosis of non-specific gastrointestinal symptoms in female subjects of reproductive age as the one reported here.