Tumor size predicts vascular invasion and histologic grade among patients undergoing resection of intrahepatic cholangiocarcinoma.

The association between tumor size and survival in patients with intrahepatic cholangiocarcinoma (ICC) undergoing surgical resection is controversial. We sought to define the incidence of major and microscopic vascular invasion relative to ICC tumor size, and identify predictors of microscopic vascular invasion in patients with ICC ≥5 cm. A total of 443 patients undergoing surgical resection for ICC between 1973 and 2011 at one of 11 participating institutions were identified. Clinical and pathologic data were evaluated using uni- and multivariate analyses. As tumor sized increased, the incidence of microscopic vascular invasion increased: <3 cm, 3.6 %; 3-5 cm, 24.7 %; 5-7 cm, 38.3 %; 7-15 cm, 32.9 %, ≥15 cm, 55.6 %; (p < 0.001). Increasing tumor size was also found to be associated with worsening tumor grade. The incidence of poorly differentiated tumors increased with increasing ICC tumor size: <3 cm, 9.7 %; 3-5 cm, 19.8 %; 5-7 cm, 24.2 %; 7-15 cm, 21.1 %; >15 cm, 31.6 % (p = 0.04). The presence of perineural invasion (odds ratio [OR] = 2.98) and regional lymph node metastasis (OR = 4.43) were independently associated with an increased risk of microscopic vascular invasion in tumors ≥5 cm (both p < 0.05). Risk of microscopic vascular invasion and worse tumor grade increased with tumor size. Large tumors likely harbor worse pathologic features; this information should be considered when determining therapy and prognosis of patients with large ICC.