Reactivity of CK7 across the spectrum of renal cell carcinomas with clear cells

Aims Current available data on cytokeratin 7 (CK7) immunostaining pattern in the clear cell renal cell carcinoma (RCC) spectrum is conflicting. The aim of this study was to assess CK7 immunoreactivity within the spectrum of clear cell renal neoplasms, including clear cell RCC, multicystic renal neoplasm of low malignant potential and clear cell papillary RCC‐like tumours. Methods and results We analysed two clones of CK7 and two tumour blocks for a total of 75 cases divided into five distinct groups: (i) low‐grade clear cell RCC, (ii) high‐grade clear cell RCC, (iii) multicystic renal neoplasm of low malignant potential, (iv) clear cell RCC with cystic changes and (v) clear cell papillary RCC‐like tumours. We found the highest CK7 reactivity in low‐grade clear cell RCC, multicystic renal neoplasm of low malignant potential and clear cell papillary RCC‐like groups, ranging from 60% to 93%. Conclusions Our findings show that CK7 immunoreactivity in clear cell RCC is variable, and the extent of staining depends on the grade and architectural growth patterns of the tumours.