[Acetone treatment of lymph node preparations in staging colorectal specimens].

Lymph node staging is the most important prognostic factor after radical surgery for colorectal carcinoma. The probability of correctly classifying a colorectal tumor increases with the number of lymph nodes harvested. This number varies with the methods used by the pathologist. An accurate examination of the surgical specimens is essential for the correct assessment of the lymph node status of the tumor. The purpose of this study was to evaluate an easy fat clearance method using pure acetone. A total of 188 surgical specimens of colorectal carcinoma were investigated. The first lymph node preparation was made using the manual method. Thereafter, the mesenteric fat tissue was treated with pure acetone for 16 h and subjected to a second lymph node examination. In 111 of the samples the required number of 12 lymph nodes for TNM classification was not reached by the manual preparation method. With the acetone treatment, 12 or more lymph nodes were found 91% of these samples (average 27 lymph nodes). In 29 samples (15%) additional lymph node metastases could be detected. In 16 samples (8% of all investigated samples) an upstaging of the pN status was necessary. This indicates the importance of our method for the optimal lymph node staging of colorectal carcinomas. Lymph node preparation after acetone treatment is an easy, low cost method resulting in a much larger number of lymph nodes for more accurate staging.