Background: To clarify the definite incidence of isolated tumor cells (ITCs) in lateral lymph nodes (LLNs) and its prognostic significance in rectal cancer patients after laparoscopic lateral lymph node dissection (lap-LLND). Methods: Consecutive rectal cancer patients who underwent standard total mesorectal excision (TME) and lap-LLND were included. All the LLNs were re-examined by hematoxylin and eosin (H&E) stain and immunohistochemistry (IHC) with a monoclonal antibody against cytokeratin 20 to confirm the status of ITCs, micrometastasis, and overt metastasis. Clinicopathological characteristics and oncological outcomes were analyzed. Results: Forty-six patients with TME and lap-LLND were included. Twelve (26.1%) patients with overt metastasis were identified. A total of 705 LLNs from 46 patients were re-examined by H&E with IHC, and ITCs were detected in 27 (3.8%) lymph nodes from 11 (23.9%) patients. No LLNs micrometastasis was found. Patients with overt metastasis had more advanced N stage and more perirectal lymph nodes metastasis. Three patients with LLNs recurrence were identified and lung metastasis was the most common metastatic site. Compared with patients with ITCs and without any metastasis, patients with overt metastasis had worse 3-year cumulative overall survival (85.7%, 83.9%, and 53.3%, respectively) and 3-year cumulative disease-free survival (85.7%, 85.2%, and 43.8%, respectively). Patients with ITCs had higher overall recurrence than patients without any metastasis (42.9% versus 11.5%, P = .035). Multivariate analysis showed that ITC status in LLNs was a significant prognostic factor (hazard ratio 2.689, 95% confidence interval 1.072-6.747; P = .035). Conclusion: ITCs in LLNs detected by the IHC method like overt metastasis detected by H&E staining contributed to higher overall recurrence.
Keywords: immunohistochemistry; isolated tumor cells; lateral lymph node dissection; micrometastasis; prognosis; rectal cancer.