Tumour-associated macrophages might represent a favourable prognostic indicator in patients with papillary renal cell carcinoma

Aims: Tumour-associated macrophages (TAM) have been reported to be regulators of progression in various human cancers. We evaluated the prognostic relevance of TAM in a large series of patients with papillary renal cell carcinoma (PRCC). Methods and results: The impact of TAM on cancer-specific survival (CSS) in 177 patients with PRCC was assessed using the Kaplan-Meier method and log-rank test. A multivariate Cox regression analysis was performed with respect to CSS. The presence of TAM was noted in 112 of 177 (63%) tumours and was associated statistically significantly with favourable pathological parameters, including low pathological T stage, node-negative tumours, low tumour grade, absence of vascular invasion and papillary subtype (all P < 0.05), respectively. Five-year CSS probabilities for patients with TAM-positive tumours were 93.5%, compared with 72.5% in patients with TAM-negative tumours, respectively (P < 0.001). Multivariate analysis revealed node-positive tumours, distant metastases and UICC stage (I versus II-IV) as independent predictors of death from PRCC, whereas the presence of TAM was associated independently with favourable outcome (hazard ratio = 0.45, 95% confidence interval 0.24-0.84, P = 0.012). Conclusions: The presence of TAM was shown independently to reduce the risk of death from cancer by 55%. The presence of TAM should therefore become part of routine pathology reporting in PRCC.