Impact of thymidine phosphorylase-expressing macrophages for surgical margin in partial nephrectomy.

Objectives: We investigated the relationship between the surgical margin in partial nephrectomy (PN) and thymidine phosphorylase (TP)-expressing macrophages in peritumoral tissue of renal cell carcinoma (RCC).

Methods: In 46 patients who underwent radical nephrectomy, we measured TP protein levels in tumor tissue, peritumoral tissue and normal tissue, and conducted immunohistochemical staining for TP and macrophages. In addition, we prospectively conducted PN with a 5-mm margin in 11 patients with pT1a RCC.

Results: The TP protein level and TP-positive macrophages were correlated with T classification, histological grade, mode of infiltration and venous invasion. However, for pT1 RCC, TP-positive macrophages in pT1a were significantly lower than in pT1b (p = 0.0140), while there was no significant difference in TP protein levels between pT1a and pT1b. No surgical margin was positive in 11 patients who underwent PN with a 5-mm margin, and no patient had local recurrence or distant metastasis during follow-up.

Conclusions: The TP protein level and TP-positive macrophages in the peritumor area are thought to be associated with tumor progression in RCC, while a similar relationship was not found in pT1a RCC. These data suggest that a 5-mm margin might be safe to reduce the risk of local recurrence when PN is performed for treatment of solitary pT1a RCC.