Lymph node 'micrometastases' and 'microinvolvement' in esophageal carcinoma

The development of new sensitive immunohistochemical methods allows the detection of single tumor cells or cell clusters in lymph nodes staged as tumor free on routine histologic examination. The prevalence and prognostic impact of these so-called lymph node 'micrometastases' has been studied in a variety of different tumor types. Only limited and still somewhat conflicting data are available for esophageal carcinoma. A differentiation between 'tumor cell microinvolvement' and true 'micrometastases' may help to clarify these controversies. While lymph node micrometastases are common even in patients with pT1 or pT2 squamous cell esophageal cancer, they appear to occur late in patients with esophageal adenocarcinoma. In contrast, tumor cell microinvolvement of lymph nodes in the absence of micrometastases seems to be more common in patients with adenocarcinoma. Periesophageal inflammation and scarring, due to the underlying chronic gastroesophageal reflux disease in patients with adenocarcinoma of the distal esophagus, may account for the apparent differences in the biology and pattern of lymph node metastases between these two esophageal tumor entities. A prognostic effect, similar to that of frank lymph node metastases, has been convincingly shown for lymph node micrometastases but not for lymph node microinvolvement. Although preliminary, these observations support the use of different strategies in lymphadenectomy for squamous cell and adenocarcinoma of the esophagus.