Giant ovarian tumor with colorectal cancer: suggestion concerning the need for colonoscopy screening in cases with large ovarian tumor-a report of three cases.

Background: Patients with giant ovarian tumor often have severe symptoms, such as abdominal distention, and the tumor tends to grow rapidly; therefore, sufficient preoperative assessments are difficult to perform. It is not always easy to differentiate between primary and metastatic ovarian cancer, especially when the ovarian tumor is huge, since a precise diagnosis of ovarian tumor depends on the histopathological findings of the excised specimen. Although metastatic ovarian tumors account for over 20% of all malignant ovarian tumors, preoperative colonoscopy is not considered a routine examination before surgery for giant ovarian tumor.

Case Presentation: We herein report 3 cases of giant (> 25 cm) ovarian tumor with colorectal cancer. All three patients visited the clinic with progressing abdominal distention, and were referred with primary ovarian malignancy. Case 1: Rectal tumor was suspected by a digital examination at the outpatient clinic, and rectal cancer was diagnosed preoperatively by colonoscopy. Computed tomography revealed a single-nodule liver tumor. Ovariectomy, rectal resection, and partial hepatectomy were performed. A histological examination revealed both primary mucinous ovarian carcinoma and rectal carcinoma with liver metastasis. Case 2: Initially, the ovarian tumor was diagnosed as primary carcinoma based on the histological findings of an incision biopsy at the previous hospital. Chemotherapy for ovarian cancer was administered without remission, and subsequently, the patient was referred to our hospital. Since the CEA level was high (142 ng/ml), colonoscopy was performed and cecal cancer was diagnosed. Ovariectomy and right colectomy were performed, and the ovarian tumor was histologically diagnosed as metastatic adenocarcinoma. Case 3: Initial ovariectomy was performed, and rectal cancer was suspected at intra-operative surveillance. Colonoscopy was performed after surgery, and rectal cancer was diagnosed. The ovarian tumor was diagnosed as metastatic adenocarcinoma. After six cycles of FOLFOX, rectal resection was performed.

Conclusion: Regrettably, two of three cases in the current series were not diagnosed with colorectal cancer at the start of treatment. This experience suggests that screening colonoscopy should be considered before treatment for every case of giant ovarian tumor.