After retrospectively reexamining the initial nephrectomy specimens, the tumour of the right kidney was also diagnosed as a mucin-poor variant of MTSCC, while the tumour of the left kidney was confirmed as a papillary RCC.<h4>Conclusions</h4>It is proposed that MTSCC can be associated with end-stage renal disease and that particularly the mucin-poor variant is easily confused with papillary renal cell carcinoma, as happened in this case. The gene discussed is MUC5AC; the disease is medical procedure.