BACKGROUND: Lymph node (LN) involvement is the most important prognostic factor in colorectal carcinomas and special methods are recommended to improve LN analysis. The objective of this study was to evaluate the impact of the use of a fat bleaching solution in LN dissection in colorectal carcinomas. METHOD: 74 adenocarcinomas (35 men - average age: 62.9) were prospectively analysed, most of them were pT3. After routine exam and LN dissection through conventional method, the fat was soaked in a solution containing alcohol (65%), ether (20%), acetic acid (5%) and formalin (10%) for 36 hours (three changes). A new dissection was performed subsequently. LN diameters were measured and the number of positive (LN+) and negative LN with < 4 mm was determined. Some LN+ obtained after the bleaching procedure were immunolabelled by AE1/AE3. RESULTS:3,167 LN (42.8/case) were dissected: 1,814 (24.5/case) by CM and 1,355 (18.3/case) after the bleaching procedure. 196 LN+ were detected: 170 (86.7%) detected by CM and 26 (13.2%) after the bleaching procedure. 1,068 (59%) of the LN conventionally dissected were < 4mm (range 0.4-23 mm) and 1,261 (93%) of the LN dissected after the bleaching procedure were < 4 mm (range 0.2-11 mm). 39/170 (22.9%) LN+ conventionally dissected were < 4 mm and 19/26 (73%) of the LN+ dissected after the bleaching procedure measured < 4 mm(p =0). The use of bleaching solution increased the numberofLN by 74.7% (p = 0.000), the detection of small LN by 118% (p = 0) and the detection of metastasis by 15.3% (p= 0.003). There was modification of pN in 5 cases (p = 0.03), from which 12-20 LN had been initially examined. 90% of all LN+ cases were detected only after the analysis of 40 LN. Conclusion: A large number of LN, mainly the small ones, must be analysed to stage colorectal cancer adequately. The use of a fat bleaching solution is inexpensive and may be a highly suitable procedure.
Colorectal cancer; Lymph node metastases; Staging; Fat bleaching solution
