Clinicopathological features of skip metastasis in colorectal cancer.

Background/aims: Japanese general rules for the staging of colorectal cancer conventionally classify lymph node metastasis into three groups according to location with respect to the primary tumor. Skip metastasis, in which distant nodes are positive but regional nodes are negative, is often encountered but poorly understood. We studied the clinicopathological features of skip metastasis in colorectal cancer.

Methodology: The location of positive nodes was classified in 323 patients with Dukes' stage C colorectal cancer. Skip n2 lymph node metastasis was defined as positive N2 metastasis without negative N1 or N3 metastasis. Clinicopathological findings and survival were compared between the patients with skip n2 metastasis (skip n2 group) and those with n1 (n1 group) or n2 metastasis (n2 group).

Results: There were 211 patients in the n1 group, 91 in the n2 group, and 21 in the skip n2 group. Pathological examination showed that the skip n2 group had fewer positive nodes than the n1 and n2 groups, but was positioned between these groups with respect to the degree of lymphatic invasion. Cumulative survival was significantly poorer in the n2 group than in the skip n2 group (p = 0.039 by log-rank test). Survival was similar in the skip n2 group and n1 group. There was also no difference in survival between patients in the skip n2 group and patients with one, two, or three N1 metastases.

Conclusions: Lymph nodes with skip n2 metastasis are most likely sentinel nodes of the primary tumor in patients with colorectal cancer. The prognosis of patients with skip n2 metastasis is therefore better than that of patients with n2 metastasis and similar to that of patients with n1 metastasis.