Pyonephrosis as a sign of sarcomatoid carcinoma of the renal pelvis.

We report the case of an urgent nephrectomy because of a pyonephrosis and sepsis due to an unsuspected sarcomatoid transitional cell carcinoma, an infrequent subtype with a bad oncological prognosis. We present a 58-year-old man assessed by internal medicine for a general syndrome and weakness many months previously. A pyonephrotic kidney was observed at abdominal computed tomography in the context of septic shock, without suspecting the underlying cause. The pathology report described a sarcomatoid transitional cell carcinoma. Sarcomatoid transitional cell carcinoma is an invasive and infrequent subtype of urothelial tumors. The symptoms are often the same as other renal masses; however, in this case, sepsis and pyonephrosis were the rare initial symptoms.