Acetone clearance of the mesocolic and mesorectal fat increases lymph node yield and may improve detection of high risk stage II colorectal cancer.

The lymph node (LN) status is key to determining the need for adjuvant therapy in colorectal cancer and for disease which has progressed to stage II (T3-T4, N0, M0. A LN yield of less than 12 is considered a risk factor similar to high grade histology, vascular, lymphatic and perineural invasion. The object of this retrospective study was to investigate the effect of acetone fat clearance of the mesocolon and mesorectum on LN yield and the identification of high risk stage II CRC patients.After conventional LN retrieval, fatty tissue derived from the mesocolon and mesorectum of 80 CRC specimens was incubated in acetone for 24 hours. A second dissection was then performed by a trained technician. Total lymph nodes as well as tumour involvement (LN pos and LN neg) were assessed at each stage. In addition, LN morphology was assessed and clinicopathological data were extracted from existing pathology reports.Eighty CRC specimens were available for study. 1548 (94%) were LNneg and 96 (6%) were LNpos. The LN yield (median and range) per specimen was 12 (3-41) increasing to 18 (4-48) after fat clearance (p<0.001). After fat clearance, 534 LNs were identified in 75 (94%) of the specimens. All but 10 were negative. The pN stage did not change in 6 patients who were found to have LNpos after fat clearance. However, the number of high risk stage II CRC patients decreased from 11 to 7. Although important for these patients, this downstaging did not reach statistical significance (p=0.125).Acetone clearance of mesocolic and mesorectal fat increases median LN yield and may in a larger study decrease the number of patients classified as high risk stage II CRC. This article is protected by copyright. All rights reserved.