Detection and relevance of immunohistochemically identifiable tumor cells in lymph nodes. 
Lymph node metastasis is a well-known feature of poor prognosis in potentially resectable solid epithelial tumors.  However, a significant number of apparently lymph node negative patients die early of metastatic disease.  Therefore, it has to be assumed that in some patients an early tumor cell dissemination has occurred which is clearly underestimated by current staging procedures.  Recently, it has been shown, that an early dissemination of individual carcinoma cells to regional lymph nodes can be detected by using sensitive immunocytochemical techniques with monoclonal antibodies against epithelium-specific proteins.  The incidence of immunohistochemically positive patients varies between 12% and 70% depending on the type of primary tumor, the immunohistochemical staining procedure used, and especially on the primary monoclonal antibody.  The detection of disseminated tumor cells in lymph nodes by immunocytochemistry is associated with a poorer prognosis in different types of epithelial tumors such as lung cancer or esophageal cancer.  The immunocytochemical method might also be useful in the detection of occult tumor cells in sentinel lymph nodes.  In conclusion, the immunohistochemical detection of disseminated tumor cells in lymph nodes can help to obtain a more exact identification of patients with an unfavorable prognosis.  Whether the identified patients will gain from an adjuvant therapy has to be evaluated in further studies.