Purpose: Detection of metastatic lymph nodes in colon cancer is essential for determining stage and, thus, therapeutic modalities. However, very small lymph nodes can easily be missed during routine examination. The aim of this study is to describe a new and easy technique for detecting tiny nodes in colonic specimens.
Methods: Thirty problematic cases, in which an unsatisfactory number of lymph nodes was found by the traditional method, were investigated. The entire mesocolonic fat was immersed for six hours in a lymph node-revealing solution (LNRS) composed of various traditional fixatives and fatty solvents. After six hours, the lymph nodes stood out as white, chalky nodules on the background of yellow fat. They were then excised, processed. and stained.
Results: Total number of lymph nodes found by the traditional method in the 30 cases was 88. After LNRS, 258 additional lymph nodes, measuring from 0.5 to 7 mm in largest diameter, were found. Of the 12 cases in which no lymph nodes were found by the traditional method, 8 became N0 and 4 became N1. Of the 14 cases first classified as N0, 4 became N1; of the 4 classified at first as N1, 2 became N2 after LNRS. Upstaging from Dukes B to C occurred in eight cases. Quality of the sections and histochemical and immunohistochemical stains after LNRS was similar to that of formalin-fixed tissues.
Conclusions: LNRS is an easy, rapid, and inexpensive technique for detecting very small lymph nodes. These may contain metastases, a fact that changes the stage of disease and influences the mode of therapy.