Immunohistochemical evaluation of tumour infiltrating mast cells in renal cell carcinomas

The aim of our study was to evaluate the relationship between the number of mast cells infiltrating the tumour and histological types of the disease and various clinicopathological parameters of prognostic importance in renal cell carcinomas. Tumour tissue blocks of 98 patients with 52 clear cell, 29 papillary and 17 chromophobe renal cell carcinomas were immunohistochemically treated with mast cell tryptase. In each case, the mast cells infiltrating the tumor were counted in 5 large magnification fields corresponding to 1 mm² in two ways: the conventional method by eyeball and the digital imaging analysis method. The relationship between mast cell counts and histological types of renal cell carcinoma and various clinicopathological parameters were evaluated. Tumour infiltrating mast cells were significantly higher in clear cell renal cell carcinomas than in papillary and chromophobe renal cell carcinomas, and in papillary renal cell carcinomas than in chromophobe renal cell carcinomas. A significant difference was found between nuclear grade and mast cell count in clear cell RCC and papillary RCC. Nuclear grade was found to be lower in cases with higher mast cell counts. There was no statistically significant difference between mast cell count and other clinicopathological parameters (age, gender, pathological tumour stage, clinical stage, tumour diameter, renal capsule invasion, perirenal fat tissue invasion, renal sinus fat tissue invasion, distant metastasis, lymphovascular invasion, sarcomatoid differentiation, rhabdoid differentiation, necrosis and mean survival). There was a strong positive correlation and statistically significant relationship between the conventional method and the digital pathology method in which we evaluated mast cell count. Our study also shows that there is a strong correlation between the conventional method for mast cell counting and digital pathology software and that digital pathology techniques can be used for standardization of these counting methods.