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The presence of lymph node metastasis is a key prognostic factor in colorectal cancer and lymph node yield is an important parameter in assessing the quality of histopathology reporting of colorectal cancer excision specimens. This study assesses the trend in lymph node evaluation over time in a single institution and the relationship with the identification of lymph node positive tumours. It compares the lymph node yield of a contemporary dataset compiled from the histopathology reports of 2178 patients who underwent surgery for primary colorectal cancer between 2005 and 2012 with that of a historic dataset compiled from the histopathology reports of 1038 patients who underwent surgery for colorectal cancer at 5 yearly intervals from 1975 to 2000. The mean lymph node yield was 14.91 in 2005 rising to 21.38 in 2012. In 2012 92.9% of all cases had at least 12 lymph nodes examined. Comparison of the mean lymph node yield and proportion of Dukes C cases shows a significant increase (Pearson correlation = 0.927, p = 0.001) in lymph node yield while there is no corresponding significant trend in the proportion of Dukes C cases (Pearson correlation = −0.138, p = 0.745). This study shows that there is increasing yield of lymph nodes from colorectal cancer excision specimens. However, this is not necessarily associated with an increase number of lymph node positive cancers. Further risk stratifying of colorectal cancer requires consideration of other pathological parameters especially the presence of extramural venous invasion and relevant biomarkers. [ABSTRACT FROM AUTHOR]

Colorectal cancer is one of the most common types of cancer with over fifty percent of patients presenting at an advanced stage. Retinoic acid is a metabolite of vitamin A and is essential for normal cell growth and aberrant retinoic acid metabolism is implicated in tumourigenesis. This study has profiled the expression of retinoic acid metabolising enzymes using a well characterised colorectal cancer tissue microarray containing 650 primary colorectal cancers, 285 lymph node metastasis and 50 normal colonic mucosal samples. Immunohistochemistry was performed on the tissue microarray using monoclonal antibodies which we have developed to the retinoic acid metabolising enzymes CYP26A1, CYP26B1, CYP26C1 and lecithin retinol acyl transferase (LRAT) using a semi-quantitative scoring scheme to assess expression. Moderate or strong expression of CYP26A1was observed in 32.5% of cancers compared to 10% of normal colonic epithelium samples (p<0.001). CYP26B1 was moderately or strongly expressed in 25.2% of tumours and was significantly less expressed in normal colonic epithelium (p<0.001). CYP26C1 was not expressed in any sample. LRAT also showed significantly increased expression in primary colorectal cancers compared with normal colonic epithelium (p<0.001). Strong CYP26B1 expression was significantly associated with poor prognosis (HR = 1.239, 95%CI = 1.104–1.390, χ2 = 15.063, p = 0.002). Strong LRAT was also associated with poorer outcome (HR = 1.321, 95%CI = 1.034–1.688, χ2 = 5.039, p = 0.025). In mismatch repair proficient tumours strong CYP26B1 (HR = 1.330, 95%CI = 1.173–1.509, χ2 = 21.493, p<0.001) and strong LRAT (HR = 1.464, 95%CI = 1.110–1.930, χ2 = 7.425, p = 0.006) were also associated with poorer prognosis. This study has shown that the retinoic acid metabolising enzymes CYP26A1, CYP26B1 and LRAT are significantly overexpressed in colorectal cancer and that CYP26B1 and LRAT are significantly associated with prognosis both in the total cohort and in those tumours which are mismatch repair proficient. CYP26B1 was independently prognostic in a multivariate model both in the whole patient cohort (HR = 1.177, 95%CI = 1.020–1.216, p = 0.026) and in mismatch repair proficient tumours (HR = 1.255, 95%CI = 1.073–1.467, p = 0.004). [ABSTRACT FROM AUTHOR]