Microscopic tumor invasion into the intra-hepatic portal vein is detected in about 20% of cases with liver metastasis from colorectal cancer [
4]. However, our review of previously reported cases revealed few instances of PVTT in the main portal branch [
8‐
14]. In fact, the reported incidence of macroscopic PVTT similar to that observed in our case report is 2.8% (4 of 142) [
9]. From January 1990 to December 2008, 231 patients underwent resection of liver metastases from primary colorectal cancer in our hospital. Of these patients, only our patient's case showed macroscopic PVTT (0.4%).
Macroscopic examination of the resected tumor in our patient did not show the preoperatively detected cystic component of the tumor. It is possible that necrotic fluid, having filled the cystic component, was absorbed and thus replaced by the tumor before removal. The resected liver tumor and PVTT macroscopically resembled HCC, which commonly develops tumor thrombi and expansive growth in the portal vein and in the hepatic vein [
17]. The capsule formation of HCC is possibly the result of mechanical compression or high inner pressure from the expansive tumor growth, thus it is also feasible that tumor thrombi might extend into the portal vein via a pressure gradient mechanism [
18]. In contrast, liver metastases from colorectal cancer are generally less commonly surrounded by a capsule compared to HCC, with one study detecting encapsulated liver metastases from colorectal cancer in only 20% of cases [
19]. The resected tumor in our patient, which was encapsulated, also resembled HCC in this point of the capsule formation. This resemblance to HCC may suggest that the PVTT in this case might have also expanded into the portal vein through a pressure gradient mechanism, as in HCC.
Table
1 summarizes 15 reported cases of liver metastasis from colorectal cancer with macroscopic PVTT, including our patient. No specific clinical features typified patients with colorectal liver metastasis and PVTT with respect to age, gender, or the primary tumor site. With regard to the stage of the primary colorectal cancer, all the primary colorectal lesions recorded were divided into T3 or T4 according to the TNM classification [
15], and lymph node metastasis was found in most of the cases (12 of 14, 86%). In 12 of the 15 cases (80%), liver metastasis was accompanied by PVTT, and the liver tumor was relatively large (60 ± 37 mm; range, 25 to 145 mm). PVTT was found metachronously in 12 patients, and synchronously with the primary tumor in the remaining three patients. Although Matsumoto
et al.[
14] suggested that survival after the operation of PVTT from colorectal cancer might depend on whether the PVTT had developed synchronously or metachronously, this suggestion seems not to be applied to the review in the present study. With regards to the liver tumor, anatomical liver resection was performed in all 15 patients. The one-year, three-year and five-year overall survival rates in the 15 cases after operation for PVTT were 64.3%, 51.4%, and 51.4%, respectively. Since this analysis was performed only in a limited number of patients, specifically successful cases, the analysis did not allow a precise general prognosis to be determined for metastatic liver tumor with PVTT. However, even if the aforementioned success bias was taken into consideration, this outcome seems to be relatively good. In general, anatomical liver resection is not usually employed for colorectal liver metastasis in contrast to HCC [
20‐
22]. However, considering that colorectal liver metastasis with PVTT is likely to spread along the portal tributaries as in HCC, it may be speculated that anatomical liver resection, which is suitable for such liver metastasis, contributes to the favorable prognosis for colorectal liver metastasis with PVTT, as suggested by some investigators [
9,
10,
14]. Today, some treatment options for colorectal liver metastasis have been established including surgery, ablation therapy, hepatic arterial infusion chemotherapy, and systemic chemotherapy, but there is no consensus for the treatment for colorectal liver metastasis accompanying PVTT. This successful case is not enough to conclude that surgery is the best treatment option for such liver metastasis, but we suggest at least that macroscopic PVTT is not a contraindication to liver surgery.