Micrometastasis and tumor cell microinvolvement of lymph nodes from esophageal squamous cell carcinoma: Frequency, associated tumor characteristics, and impact on prognosis

BACKGROUND. The purpose of this study was to investigate micrometastasis (MM) and tumor cell microinvolvement (TCM) in the regional lymph nodes of patients with esophageal squamous cell carcinoma (SCC). METHODS. MM was defined as individual tumor cells or tumor cell clusters <0.5 mm in greatest dimension with a surrounding stromal reaction. TCM was defined as individual tumor cells or tumor cell clusters without a surrounding stromal reaction. One thousand nine hundred and fifty-four lymph nodes were dissected from 69 complete (R0) resection specimens of TNM classified pT1-3, pN0 or pN1, and M0 esophageal SCC. These lymph nodes were examined immunohistochemically using the monoclonal antibody cocktail AE1/AE3 for cytokeratins. The primary tumors were immunostained with an anti-E-cadherin monoclonal antibody. RESULTS. MM ± TCM was found in 13 cases (31.7%) and TCM alone in 2 cases (4.9%) of the 41 pN0 cases. The pN0 patients with MM (but not TCM) had the same shorter survival as the original pN1 cases (P < 0.05). Of the 69 primary tumors. 49 (71.0%) had reduced or negative E-cadherin expression that showed a correlation with the occurrence of lymph node metastases (original pN1), MM, and TCM, but not prognosis. CONCLUSIONS. The results of the current study show that, in SCC of the esophagus, MM, but not TCM, in the regional lymph nodes is prognostically equivalent to metastasis and should be examined by immunohistochemistry to classify these cases correctly as pN1.