Dear Editor:

Ovarian carcinoma is the most lethal gynecological cancer [1], and the endometrioid type accounts for 7–20 % of all cases [2]. The gastrointestinal stromal tumor (GIST) may mimic ovarian tumors, as reported previously by other authors [3, 4]. We present a case report of a GIST mimicking an ovarian carcinoma.

A 67-year-old female underwent a colonoscopy for colon cancer screening. It showed a submucosal lesion, covered with normal appearance mucosa. An endoscopic ultrasonography showed between 4 and 14 cm from the anal margin, with the greatest transverse diameter of 42.5 by 32.7 mm, a heterogeneous lesion, hypoechoic, with slightly irregular borders, originated in the muscular layer; the luminal board counter presented itself closely adjacent to an ovary, where it was identified as a cystic lesion, and a loss of the cleavage plane. We identified a perilesional, oval, hypoechoic adenopathy, with a diameter of 11 by 5.2 mm. We suspected of a GIST or an extraintestinal tumor involving the rectum. An endoscopic ultrasonography (EUS) with fine needle (19G) aspiration with collection of sampling for histology and cytology revealed high-grade undifferentiated neoplasm suggestive of ovarian carcinoma, CD117 negative.

She underwent a surgery that confirmed an endometrioid ovarian carcinoma, invading the rectum. Subsequently, the patient has started chemotherapy with carboplatin and paclitaxel and is still on treatment.

Besides, there have been reported a case of primary epithelial ovarian carcinoma with gastric metastasis mimicking GIST, but to our best knowledge, there have not been reported an ovarian cancer mimicking a rectal GIST.

We emphasize the high accuracy of EUS in the correct characterization of the lesion and its anatomical relations and the possibility of collecting a sample that confirms the diagnosis, allowing a more guided surgery.