Effect of modified Davidson's fixative on examined number of lymph nodes and TNM-stage in colon carcinoma.

AIMS We evaluated the effect of modified Davidson's fixative (mDF) on the number of lymph nodes examined and staging in patients with colon carcinoma. METHODS The results of two different fixation methods used in the pathological preparation of the resection specimens were analyzed. A traditional formalin preparation with manual dissection of all nodes was performed in 117 colon specimens between January 2003 and July 2004. After July 2004, the resected specimens of 125 patients was fixated in mDF. Differences in the retrieval and number of nodes and size of suspected nodal metastases were measured. All lymph nodes were stained with conventional H&E methods. RESULTS The median number of examined nodes increased from 5 (0-17) to 13 (0-35) nodes after the introduction of mDF (p<0.001). The type of resection and the T-stage influenced the number of retrieved nodes significantly. The percentage of node-positive cases increased from 30% to 41% (p=0.077) with mDF, the median size of the retrieved lymph nodes decreased from 9 mm before to 6 mm after mDF (p<0.001) and more micrometastases were found (6% vs. 16%, p=0.03). CONCLUSIONS With mDF technique more lymph nodes were retrieved in the resected colon specimens. Smaller nodes and more micrometastases were found, leading to more node positive patients.