Clinicopathological significance of microscopic abscess formation at the invasive margin of advanced low rectal cancer

Background: The aim of this study was to evaluate the clinicopathological significance of microscopic abscess formation (MAF) at the invasive front of advanced low rectal cancer. Methods: The clinicopathological features of 226 consecutive patients with low rectal cancer, who underwent curative resection between May 1997 and December 2002, were analysed. Results: Fifty-seven (25.2 per cent) of the 226 tumours had MAF and 169 (74.8 per cent) did not. Patients with tumours showing MAF were more likely to have extended surgery than those without MAF: 47 versus 31.4 per cent respectively underwent non-sphincter-preserving surgery (P = 0.029) and 82 versus 60.9 per cent underwent lateral lymph node dissection (P = 0.003). The incidence of lymph node metastases was lower in patients with MAF (30 versus 53.3 per cent; P = 0.002). Univariable analysis of disease-free survival revealed that depth of invasion (P < 0.001), lymph node status (P < 0.001), histological type (P = 0.035), lymphatic invasion (P < 0.001), venous invasion (P < 0.001), perineural invasion (P < 0.001), focal dedifferentiation (P < 0.001) and MAF (P < 0.001) were significant prognostic factors. Multivariable analysis showed that lymph node status (P < 0.001), perineural invasion (P = 0.002), venous invasion (P = 0.033) and MAF (P = 0.012) remained independent prognostic factors. Conclusion: MAY may reflect indolent tumour behaviour and a more favourable outcome in patients with advanced low rectal cancer.