Micro Metastasis in Lymph Nodes After Colectomy for Colonic Cancer
The detection of micro metastasis in lymph nodes after colectomy for colonic cancer indicates locally advanced disease (stage III), which has important prognostic implications and necessitates adjuvant chemotherapy consideration. 1
Definition and Classification
- Micro metastasis refers to small tumor deposits measuring >0.2 mm but <2 mm in lymph nodes
- Distinguished from isolated tumor cells (ITCs), which are single cells or small clusters <0.2 mm
- According to AJCC staging, micro metastasis is classified as node-positive disease (N1)
- The presence of micro metastasis upstages the cancer from Stage II (node-negative) to Stage III (node-positive) with TNM classification of pT(x)N1M0 2
Detection Methods
- Standard H&E staining may miss micro metastasis
- Detection often requires:
- Immunohistochemistry (IHC) for cytokeratin
- Multiple sections of lymph nodes
- Examination of sentinel lymph nodes
- At least 12 lymph nodes should be examined to accurately stage colon cancer 2, 1
Prognostic Implications
- Micro metastasis indicates locally advanced disease with poorer prognosis compared to truly node-negative disease 1
- Patients with micro metastasis have decreased disease-free and overall survival compared to node-negative patients 3
- The NCCN guidelines emphasize that proper lymph node evaluation is critical for accurate staging, with at least 12 lymph nodes needed to establish stage II colon cancer 2
- Inadequate lymph node sampling may lead to understaging and inappropriate treatment decisions 2
Treatment Implications
- Patients with micro metastasis are candidates for adjuvant chemotherapy 1
- The presence of nodal involvement is a key factor in determining the need for adjuvant treatment
- The AJCC and College of American Pathologists recommend examination of a minimum of 12 lymph nodes to accurately identify stage II colorectal cancers 2
- If fewer than 12 lymph nodes are identified, it is recommended that the pathologist reexamine the specimen for additional lymph nodes 2
Controversies and Considerations
- Some studies have shown conflicting results regarding the prognostic significance of micro metastasis
- Bilchik et al. found that all patients with colon cancer recurrences had a positive sentinel node by either H&E/IHC or qRT-PCR, suggesting clinical relevance 3
- However, Nakanishi et al. found that the number and level of positive micrometastatic lymph nodes was significantly correlated with postoperative recurrence 4
- Conversely, Choi et al. found that micrometastases detected by immunohistochemical staining were not useful for identifying stage II patients at higher risk for relapse 5
The detection of micro metastasis in lymph nodes after colectomy for colonic cancer represents locally advanced disease with implications for both prognosis and treatment decisions. Thorough lymph node evaluation is essential for accurate staging and appropriate management planning.