We encountered three cases of giant ovarian tumor with coexisting colorectal cancer. Two of them had metastatic ovarian carcinoma of colorectal origin, and the other had primary ovarian cancer. Regrettably, two of the three cases had not been diagnosed with colorectal cancer at the start of treatment.
Making a preoperative diagnosis of ovarian tumor is often challenging and difficult, since patients with giant ovarian tumor include not only those with primary ovarian carcinoma but also those with metastatic tumor and pathologically benign tumor mimicking malignancy [8,9,10]. Metastatic ovarian tumors have been reported to account for over 20–30% of all malignant ovarian tumors [1, 2]. Colorectal cancer account for 65% of ovarian metastases, with an increasing percentage reported in recent years [1, 3, 11]. Conversely, ovarian metastases occur in 5–10% of women with metastatic colorectal cancer [12]. Most of the giant ovarian tumors reported were more than 25 cm in diameter [6, 9, 10, 13]. A pre-treatment differential diagnosis between primary ovarian cancer and metastatic tumor is more difficult when the ovarian tumor is huge [5], since severe symptoms such as abdominal distention and progressive tumor growth, may hinder further examinations and limit the time for a preoperative assessment. Some radiologists claim that a mixed cystic and solid ovarian mass should be regarded as a metastatic tumor, especially in patients with a history of colorectal cancer [14]; however, other authors insist that depending on radiographic studies is inadequate for differentiating between primary and metastatic ovarian tumors [12]. Presently, a precise diagnosis of ovarian tumor depends on the histopathological findings of excised specimen. An immunohistochemical evaluation is essential for distinguishing between primary and metastatic ovarian carcinoma [6]. Colorectal carcinomas are generally negative for CK7 but positive for CK20 and CDX2, whereas primary ovarian cancers are mostly (> 90%) positive for CK7 and negative for CK20 and CDX2 [11].
Although resection of malignant ovarian tumor can provide a survival benefit for both primary ovarian carcinoma and metastatic ovarian carcinoma originating from colorectal cancer, the operative procedures differ greatly, depending on whether the case is one of primary or metastatic ovarian cancer. Extended surgery, including hysterectomy, omentectomy, and lymph node dissection is needed for primary ovarian cancer surgery [15]. Furthermore, neoadjuvant chemotherapy, is often administered prior to surgery for ovarian cancer [2, 16]. Therefore, pre-treatment detection of colorectal cancer is crucial for deciding on a treatment strategy, so adequate chemotherapy regimens should be chosen depending on the primary tumor [17]. Case 2 in the present study was initially misdiagnosed as primary ovarian carcinoma based on the histological findings of an incision biopsy made at the previous hospital without an immunohistochemical study. Screening colonoscopy was not performed despite the elevated serum CEA level. As a result, neoadjuvant chemotherapy for ovarian cancer was mistakenly administered, without remission. The patient was treated improperly for 6 months before she was referred to our hospital and underwent colonoscopy. These facts indicate that an adequate diagnosis at the start of treatment is essential for achieving the best treatment outcomes.
Regrettably, two of the three cases in the current case series had not been diagnosed with colorectal cancer at the start of treatment. Although colonoscopy is a gold standard in evaluating the presence of colorectal malignancy, screening colonoscopy is not considered required as a preoperative investigation for primary ovarian cancer [5, 7]. As a result, in actual clinical practice, patients with metastatic ovarian cancer originating from colorectal cancer often undergo surgery based on a misdiagnosis of primary ovarian malignancy. Saltzman et al. reported that 5 of 212 (2%) gynecologic oncology patients had been diagnosed with colorectal cancer at pre-treatment screening colonoscopy; however, they concluded that colon screening was not necessary in the preoperative workup of gynecologic oncology patients [7]. Renaud et al. reported that 7% had a primary GI cancer in their case series of 71 ovarian malignancies [3]. Ravizza et al. concluded that colonoscopy identified a not insignificant number of patients requiring colorectal surgery. In their prospective study of 144 consecutive patients with a supposed primary ovarian cancer, 6 (4%) patients were diagnosed with colorectal cancer metastatic to the ovary. Furthermore, 8 (6%) patients were diagnosed with bowel infiltration at screening colonoscopy [18]. Preoperative computed tomography dedicated to examining the bowel may be a viable alternative to colonoscopy, but not completely [8]. Given that colon cancer is by far more frequent than ovarian carcinoma, screening colonoscopy should be considered necessary in every case of giant ovarian tumor before treatment.
This case series demonstrates that screening colonoscopy should be considered routinely before treatment for cases of giant ovarian tumor, and multidisciplinary approach is important in order to make the right diagnosis and offer the best treatment.