Lymph node micro-metastasis: an investigation, including three-dimensional reconstruction

The mechanism by which malignant cells metastasis to, and colonise, regional lymph nodes is not known. In an attempt to characterise micro-deposits an affected lymph node associated with a primary intra-oral squamous cell carcinoma was studied. Three-dimensional reconstructions of the node and micro-tumour were made and the relationships and distribution of apparently isolated malignant cells present within the node studied. Semi-serial ethanol-fixed paraffin was sections of the node were stained with monoclonal antibody AE3 (cytokeratin). Outlines of the node and occupying micro-tumour were traced onto polystyrene tiles and onto acetate sheets, permitting the construction of both a solid and a transparent three-dimensional model. Additionally, the positions of apparently 'isolated' AE3-positive malignant cells were noted. The solid reconstruction showed that the micro-tumour deposit grew most quickly into the node via the septa and more slowly around the subcapsular region. The transparent reconstruction was less useful. Most isolated, individual malignant cells were found in the peripheral margin of the node.