The clinical significance of lymph node micrometastasis in stage I and stage II colorectal cancer.

Aim: Recent advances in immunohistochemical techniques have made it possible to identify micrometastasis using antibodies to cytokeratins (CK). The aim of the study was to determine the prevalence and prognostic significance of immunohistochemically detected micrometastasis (IHM) in patients with localised colorectal cancer (CRC) (Dukes' A and B). A further aim was to study the prognostic role of histopathological factors such as vascular invasion.

Methods: The original histology of 168 consecutive patients with Dukes' A or B tumours who had undergone curative resection was reviewed. Immunohistochemical staining was performed using CK antibodies, AE1/AE3 and MNF116 on all (n=898) lymph nodes. Survival analysis was performed on 105 cases that had been followed up until death or for at least 5 years.

Results: IHM were detected in 17.3% of lymph nodes analysed. Adverse outcome (death/local recurrence) was recorded in 8/49 (16%) patients with IHD-positive nodes and in 10/56 (18%) patients negative for IHM. IHM was not associated with adverse outcome on either univariate (p=0.540) or multivariate analyses (p=0.673). There was no correlation of IHM with age, gender, site, size and grade of tumour, depth of tumour invasion or perineural and vascular invasion. Vascular invasion was the only independent prognostic factor identified.

Discussion: We have shown that isolated CK-positive epithelioid cells are commonly found in morphologically benign pericolic lymph nodes of patients with localised (Dukes' A or B) CRC. These cells may represent occult micrometastasis but are not clinically significant. Vascular invasion identifies patients with localised CRC likely to develop recurrences or die of disease.