The purpose of this study was to investigate whether the presence of lymph node micrometastasis in pathological lymph node-negative (pN0) oesophageal squamous cell carcinoma had prognostic value. Some 1840 lymph nodes were obtained from 50 patients with pN0 oesophageal squamous cell carcinoma who underwent curative resection of the primary tumour with systematic lymphadenectomy. These lymph nodes were examined immunohistochemically with anticytokeratin antibody (AE1/AE3). Lymph node micrometastases newly detected by immunohistochemistry were classified as micrometastasis. Additionally, lymph node micrometastases were classified into three stages: stage 1, one individual AE1/AE3-positive cell; stage 2, multiple individual positive cells; stage 3, one or multiple positive clusters. Micrometastases were detected in 20 patients (40 per cent). A higher stage of micrometastasis was associated with greater pathological tumour (pT) size (P = 0.023). Recurrent tumours developed in nine patients. However, the frequency of recurrence was similar in patients with, or without, micrometastasis (five of 20 and four of 30 patients respectively; P = 0.25). Twenty-three of 30 patients without micrometastasis survived, whereas 15 of 20 patients with micrometastasis were still alive (5-year overall survival 75 and 78 percent respectively, P = 0.91). Twenty-six of 30 patients without micrometastasis had no recurrence, whereas 15 of 20 patients with micrometastasis had no recurrence (5-year relapse-free survival 86 and 73 per cent respectively, P = 0.37). There was no significant difference in prognosis with respect to the stages of micrometastasis. Multivariate analysis also showed that micrometastasis was not an independent prognostic factor (P = 0.73). Immunohistochemical detection of lymph node micrometastasis may be an indicator of lymphatic dissemination of tumour cells. However, the presence of micrometastasis had no impact on the prognosis of node-negative patients with oesophageal squamous cell carcinoma.
