Incidence and prognostic significance of occult tumor cells in lymph nodes from patients with stage IIA colorectal carcinoma

Approximately 30% of patients with lymph node (LN)-negative colorectal carcinoma (CRC) die of tumor recurrence, which can be related to the presence of tumor cells in LNs not detected by conventional histopathologic analysis. However, the prognostic significance of occult cancer cells still remains uncertain. We evaluated the incidence and the prognostic significance of occult cancer cells in LNs from 395 consecutive patients with curatively resected stage IIA CRC using immunohistochemistry for cytokeratin 20. Immunostained tumor cells were categorized as micrometastases (MCMs) or isolated tumor cells (ITCs) according to the American Joint Committee on Cancer criteria. The detection rates were compared with the clinicopathologic characteristics of the patients and with cancer-specific survival. The median follow-up time was 128 months. Micrometastases were detected in 39 patients (9.9%), whereas ITCs were found in 112 (28.4%), for an overall frequency of 38.2%. None of the clinicopathologic parameters examined was correlated with the presence of occult cancer cells. Patients with ITCs and those with negative LNs showed a similar survival rate (77.7% and 78.3%, respectively), whereas patients with MCMs had a lower survival rate (64.1%). At the univariate analysis, MCMs, tumor growth pattern, extent of tumor spread, and Crohn's-like lymphoid reaction influenced the survival rate significantly. Nevertheless, at the multivariate analysis, only the pattern of tumor growth and the extent of tumor spread were independent prognostic factors. The detection of immunostained tumor cells in the LNs of patients with stage IIA CRC occurs relatively frequently but has no significant effect on prognosis.