An immunohistochemical study of occult micrometastases in regional lymph nodes of patients with stage I non-small cell lung carcinoma]

739 regional lymph nodes from 94 patients with stage I non-small cell lung carcinoma (NSCLC) were studied by immunohistochemistry. These lymph nodes, contained no metastasis as assessed by conventional histopathology, were recut. A series consecutive sections from the original blocks were immunostained with polyclonal and monoclonal antibodies to keratins, carcinoembryonic antigen (CEA) and human milk fat globulin membrane antigen (HMFG-2). Single tumor cells or small clusters of tumor cells, not visible on routine examination, were readily detected. The actual number of lymph nodes that contained occult tumor cells was 123 (16.6%) from 53 patients (56.4%). The majority of 102 immunostaining positive nodes were distributed in the hilar (29%) and peribronchial (25%) regions. Our data indicate that: 1. a series consecutive sections and immunohistochemistry may greatly increase the diagnostic yield of occult micrometastases in lymph nodes. 2. the high incidence of occult metastases in NSCLC may be of importance in relation to their rapid dissemination and high death rate. 3. the high frequency of occult nodal metastases in NSCLC raises questions in regard to our presently used criteria for staging, prognosis and treatment of ostensibly stage I disease. 4. perhaps resections of hilar and peribronchial lymph nodes will have an important clinical significance in prevention of wide dissemination of tumor cells.