A case of ascending colon cancer accompanied with tumor thrombosis in the superior mesenteric vein treated with right hemicolectomy and greater saphenous vein grafting

Highlights • The occurrence of colorectal cancer with tumor thrombosis in the mesenteric vein is very rare.• Complete resection of the primary cancer with tumor thrombosis is essential.• Combined surgery and chemotherapy should be performed to prevent recurrence.


Introduction
Colorectal cancer accompanied with tumor thrombosis in the superior/inferior mesenteric vein (SMV/IMV) is quite rare [1]. Otani et al. in their review article showed that venous tumor thrombosis may be a strong risk factor for the development of liver metastasis [2]; hence, the presence of venous tumor thrombosis may influence the patient's survival. Surgical thrombectomy and complete resection of the primary cancer should be considered for a better prognosis [1,3]. We present a case of tumor thrombosis in the SMV Abbreviations: SMV, superior mesenteric vein; IMV, inferior mesenteric vein; CT, computed tomography; CEA, carcinoembryonic antigen; CA 19-9, cancer antigen 19-9; PET, positron emission tomography; FDG, fluorodeoxyglucose; SUV, standardized uptake value; ICV, ileocolic vein.
* that was treated with right hemicolectomy and greater saphenous vein grafting. To the best of our knowledge, this is the first case report of venous tumor thrombosis due to colorectal cancer that was treated by vein grafting. This work has been reported in line with the SCARE criteria [4].

Presentation of case
A 48-year-old woman was initially admitted to a nearby hospital due to anemia. Total colonoscopy and computed tomography (CT) revealed ascending colon cancer accompanied with tumor thrombosis in the SMV. Subsequently, the patient was referred to our department for surgical treatment.
Her medical history was unremarkable. Complete blood count showed white blood cell count and hemoglobin level of 7850/l and 12.1 g/dL, respectively. Serum biochemistry test results were as follows: aspartate aminotransferase, 17 U/L; alanine aminotransferase, 19 U/L; total bilirubin, 0.1 mg/dL; carcinoembryonic antigen, 341.9 ng/mL; cancer antigen 19-9, 3 U/mL; and C-reactive protein, 0.18 mg/dL. The coagulation marker D-dimer level was 0.7 g/mL.
Total colonoscopy revealed a type 2 tumor in the ascending colon, and moderately differentiated adenocarcinoma was diagnosed by examining the biopsy specimen (Fig. 1a).   and an intraluminal filling defect from the ileocolic vein to the SMV (Figs. 1b and 2a). On positron emission tomography-computed tomography (PET-CT), abnormal fluorodeoxyglucose (FDG) uptake was observed in the ascending colon (SUV-max: 23.1). Abnormal FDG uptake extended from the ileocolic vein to the SMV (SUV-max: 9.4) (Fig. 2b).
The patient was diagnosed with ascending colon cancer with tumor thrombosis in the SMV. The preoperative staging was T4aN1M0, stage IIIB (TNM classification). After admission, preoperative pharmacological prophylaxis was initiated with unfractionated heparin (15,000 unit/day) to prevent extension of thrombosis. Surgical resection was performed on the sixth inpatient day. Tumor thrombosis extended from the ileocolic vein to the root of the SMV. Right hemicolectomy with D3 lymphadenectomy, tumor thrombectomy of the SMV, and greater saphenous vein grafting were performed (Fig. 3). The duration of surgery was 334 min, and the blood loss was 210 mL.
Pathological examination showed that the tumor was a moderately differentiated adenocarcinoma of the ascending colon, which reached the subserosal layer, with no lymph node metastasis (0/35) or lymphatic duct involvement (ly0) but with venous involvement (v2) (Fig. 4). The pathological staging was T3N0M0, stage IIA (TNM classification). Contrast-enhanced CT was performed to confirm patency of the reconstructed vein on the seventh postoperative day. Remnant tumor thrombosis or vein stricture was not detected in the CT image (Fig. 5a). The postoperative course was uneventful, and the patient was discharged on the eighth postoperative day. Eight courses of chemotherapy with capecitabine plus oxaliplatin were initiated 6 weeks postoperatively and continued for 6 months. Currently, 17 months have passed after the surgery, and no recurrence has been detected to date (Fig. 5b).

Discussion
Intraluminal tumor thrombus in the mesenteric vein originating from colorectal cancer is a rare condition [1]. Sato et al. reported that the incidence of advanced colorectal carcinoma with venous tumor thrombosis was 1.7% [5]. In contrast, tumor thrombosis in the portal vein system is a frequent complication of hepatocellular carcinoma because of its hypervascularization [1]. Otani et al.    reported that the number of reports on venous tumor thrombosis is increasing owing to the advancement of diagnostic imaging technology [2]. 18F-FDG-PET may be useful for the differential diagnosis between tumor thrombus and venous thrombus [6]. Table 1 shows the reported cases of colon cancer accompanied with tumor thrombosis in the SMV and IMV in the Japanese population [3,[7][8][9][10][11][12][13][14][15]. Including our case, seven and five cases in the SMV and the IMV, respectively, have been reported. Based on the reported cases, the ascending colon and the rectum were the most common tumor sites developing tumor thrombosis. With regard to SMV tumor thrombosis, the most common histological type was moderately differentiated adenocarcinoma (five of seven cases). After surgical treatment, liver metastatic recurrence occurred in four of 12 cases (25%). Given this, venous tumor thrombosis is likely to increase the risk of liver metastasis from primary colorectal cancer. Considering micrometastasis, adjuvant chemotherapy should be performed even after complete surgical tumor resection [2,13].
Before surgical treatment, accurate assessment of the range of tumor thrombosis and collateral circulation in contrast-enhanced CT is necessary [8]. Initial ligation of the center side vein may be essential to prevent migration of tumor thrombosis [2,7].
In the surgical treatment of tumor thrombosis in the SMV, which is a requisite drainage vein of the small bowel, we need to consider short bowel syndrome [13]. We were able to perform thrombectomy close to the root of the SMV using the greater saphenous vein graft. Massive small bowel resection was avoided by this procedure. To the best of our knowledge, this is the first case report of venous tumor thrombosis due to colorectal cancer treated by vein grafting.

Conclusion
Here, we present a case of ascending colon cancer accompanied with tumor thrombosis in the SMV that was treated with right hemicolectomy and greater saphenous vein grafting. In cases of venous tumor thrombosis, a well-planned surgical strategy and systemic chemotherapy are required for a better prognosis.

Provenance and peer review
Not commissioned, externally peer-reviewed.