Tumour budding and other prognostic pathological features at invasive margins in serrated colorectal adenocarcinoma: a comparative study with conventional carcinoma

Aims: To assess the incidence of tumour budding (TB), cytoplasmic pseudo-fragments (CyPs), tumour growth pattern (TGP) and peritumoural lymphocytic infiltration (PLI) in a series of serrated adenocarcinoma (SAC) and conventional carcinomas (CCs) of the colorectum in order to ascertain whether such features could explain the worse prognosis of SAC and whether they have prognostic value in SACs. Methods and results: Tumour budding, CyPs, TGP and PLI were evaluated in 81 SACs and 81 matched CCs. Kaplan-Meier survival curves and Cox logistic regression analysis were obtained for histological parameters. SACs had more high-grade (HG) TB (HG-TB) (69.1%), HG-CyPs (47%), infiltrative TGP (42%) and weak PLI (W-PLI) (65.4%) than CCs (40.7%, P = 0.0003; 19.7%, P = 0.0002; 29.7%, P = 0.07; 45.7%, P = 0.0087). SACs with HG-TB (P = 0.017), HG-CyPs (P = 0.045), infiltrating TGP (P < 0.001) and W-PLI (P = 0.04) had a worse 5-year survival, as had SACs with infiltrating TGP (P = 0.047) and W-PLI (P = 0.04) compared with CCs. For SACs, infiltrative TGP and W-PLI were independent prognostic parameters on multivariate analysis, as was location and regional node status. Conclusion: Compared to CC, SAC displayed more HG-TB, HG-CyPs and fewer PLI at the invasive margins and this may account for its poorer clinical outcome. TB, CyPs, TGP and PLI are useful histological prognostic aids in SAC.