In patients with squamous cell carcinoma of the esophagus, the preoperative clinical staging of the N category is primarily based on the lymph node size. Lymph nodes > 10 mm are considered to be tumor-infiltrated. This histopathologic study investigated the correlation of lymph node size and metastatic infiltration in esophageal carcinoma of patients with and without neoadjuvant radiochemotherapy. The specimens of 40 patients with squamous cell carcinoma of the esophagus were included in a prospective morphometric study. Half of these patients (n = 20) received preoperative radiochemotherapy. The number of resected lymph nodes were counted, and the largest diameter of each node was measured. Metastatic involvement of each node was analyzed by histologic examination. The frequency of lymph node metastases was calculated and correlated to the lymph node size. A total of 1196 lymph nodes with an average of 29.9 nodes per patient were resected and analyzed; 129 lymph nodes (10.8%) showed metastatic infiltration. The average size of 1067 tumor-free lymph nodes was 5.1 +/- 3.8 mm in maximum diameter, whereas the average size of 129 metastatic lymph nodes was 6.7 +/- 4.2 mm (p = 0.00006). Of all resected lymph nodes, 761 (63.6%) were < or = 5 mm in maximum diameter. Only 9.3% (n = 111) of all resected lymph nodes were > 10 mm in maximum diameter. There was no significant correlation between lymph node size and the frequency of nodal metastases. No difference in size could be demonstrated between patients with and without neoadjuvant radiochemotherapy. Diagnostic imaging techniques using size as the criterion of nodal infiltration cannot exactly assess the nodal status of patients with esophageal carcinoma. This is also true for patients after neoadjuvant radiochemotherapy. Therefore, evaluation of the nodal status in patients with squamous cell carcinoma of the esophagus is entirely based on pathohistologic analysis after a well defined lymphadenectomy.