Total Mesocolon Examination in Colon Cancer
Following this policy in 400 consecutive cases of T2 and T3 colon cancers, we observed in 6 cases (1.5%) microskip secondary lesions in lymphatic structures at the mesenteric root, in proximity with the lumboaortic stations. This agrees with the particular arrangement of the lymphatic network of the mesocolon, where the capillaries are predominant and through numerous interconnections open different and unexpected ways to lymph drainage, under the action of different and variable external forces.2 In 2 cases, the secondary microskip metastases were placed in newly formed lymphatic capillaries, suggesting that the neolymphangiogenesis, induced by the tumor, favors implantation of metastases.3
Interestingly, in 2 patients the microskip metastases appeared to be located inside mesocolic lymphatic aggregates, where lymphocytes CD20+ B prevail on the CD4+ T-helper and CD8+ T-cytotoxic cells. These structures, already present in the normal mesocolon and in the greater omentum, lack proper capsule and follicular organization.4,5 In patients with colon cancer, they can increase in number and show a progressive evolution toward proper lymph nodes; we interpret this as a sign of immunological reaction against the tumor.