Metastatic patterns of renal carcinoma: an analysis of 687 necropsies.

The metastatic behaviour of renal cell carcinoma has been studied in a series of 687 necropsies. The observations were consistent with the concept of "metastatic inefficiency", in that in 295 cases, including 25 with renal vein invasion, there were no detectable metastases. In the present series, renal vein involvement was not an important prognostic factor in stage 1 or 2 disease. In 73% of cases without lung metastases there were none in other sites, and in 84% of those with lung metastases there were others elsewhere, consistent with a metastatic "cascade" in which metastases first developed in the lungs and were later detected in other organs. However, the observations did not permit discrimination between anatomic cascades, in which other organs were seeded from metastasizing pulmonary metastases, and temporal cascades, in which the other were seeded at the same time as the lungs, but with fewer cancer cells. The patterns of arterial metastasis were consistent with the "seed-and-soil" hypothesis, and a novel index was developed to quantify differential organ "soils". The contralateral kidney was not the best soil for metastases from renal carcinoma. Given the presence of lymph node metastasis, the probability of heamatogenous metastasis is 90%. However, in the absence of nodal metastasis, approximately half the cases had haematogenous metastasis.