Synchronous colonic metastasis of sarcomatoid chromophobe renal cell carcinoma. Diagnostic challenges and value of CD10 and vimentin immunostains in diagnosis

In chromophobe renal cell carcinoma (CRCC), sarcomatoid and rhabdoid features denote a dismal prognosis, a short time to recurrence, and metastatic disease after nephrectomy. A 58-year-old male presented for management of a septic shock secondary to stercoral peritonitis. Four months before, he underwent a right nephrectomy for a lower polar renal tumor. The final diagnosis concluded to a pT4 CRCC with extensive sarcomatoid and rhabdoid changes. An abdominal CT-scan objectified a heterogeneous colon mass without renal recurrence. Urgently, the patient underwent right hemicolectomy and segment-VI hepatectomy. Histology suggested high-grade sarcoma with undifferentiated tumor proliferation and a lack of well-differentiated epithelial component. Immunohistochemistry (IHC) confirmed the renal origin of the colon metastasis, which consisted solely of the dedifferentiated component of CRCC. Tumors originating from the kidney should be considered in the differential diagnosis of undifferentiated colorectal cancers. An excellent anatomo-clinical correlation and a suitable IHC workup would reveal the appropriate diagnosis.