Partial regression of conventional renal cell carcinoma displays markers of wound repair.

AIMS: During detailed analysis of H&E-stained histological slides of 710 unbiased conventional renal cell carcinomas (cRCCs), 141 tumours displayed partial regressive changes showing strong similarity to that of wound healing. We aimed to analyse the molecular processes occurring in regressive tumours. METHODS: Immunohistochemistry was applied to analyse the signalling molecules in 12 selected tumours, and statistical analysis was used to estimate the correlation between regression and the outcome of the disease. RESULTS: The regressive areas displayed inflammatory granulation tissue expressing transforming growth factor beta-1 (TGFB1), interleukin-1 beta and interleukin-6 (IL1B and IL6), proliferation of alpha smooth muscle actin (αSMA) positive naïve activated fibroblasts and a diffuse fibronectin 1 (FN1) network. In the central areas of regressive tissues, parallel-running myofibroblasts showed FN1, collagen type I alpha 1 (COL1A1) and collagen type III alpha 1 (COL3A1) positive immunoreaction. Partial tumour regression is associated with a better postoperative course of the disease. CONCLUSIONS: Partial regression is a frequent event in cRCCs. Recognising complex molecular processes involved in tumour regression might help to find a way towards 'healing' cRCC.