A comparative study of metastatic renal cell carcinoma with correlation to subtype and primary tumor.

Clear cell (CRCC), papillary (PRCC) and chromophobe (CHRC) renal cell carcinoma (RCC) are the three most frequent subtypes of RCC. The rate and distribution of their metastatic lesions have not been well documented. We compared metastatic RCC according to subtype and primary tumor characteristics to better understand their behavior and to aid in the diagnosis of metastatic RCC. Pathology reports and clinical charts related to 283 CRCC, 48 PRCC and 13 CHRCC, including their respective sarcomatoid variants, were reviewed. A hundred and thirty-seven CRCC, 5 PRCC and 1 CHRCC with metastases were identified. CRCC and non-CRCC (PRCC and CHRCC) had different patterns of metastasis and primary tumor growth. CRCC metastases were predominantly distributed in lungs, bone, brain, lymph nodes, and adrenal glands. The associated primary CRCC measured 1.5 to 15 cm, were of all grades and stages, and were often associated with invasion of small or large veins. Three PRCC had regional lymph node metastases, 1 PRCC had both regional and mediastinal lymph node metastases. Bone metastasis was present in 1 case each of PRCC and CHRCC. One PRCC with metastasis solely to regional nodes measured 4 cm. The other 4 cases of PRCC with regional lymph node and/or distant metastases as well as the CHRCC with distant metastases were greater than 8 cm in diameter. In metastasizing and non-metastasizing non-CRCC, invasion of small veins was rare and invasion of renal veins was not seen. We cannot comment with any certainty on the metastatic behavior of CHRCC. In our experience, PRCC tend to loco-regional invasion with lymph node spread. They have a low potential for vascular invasion and distant metastases that likely occur only at late stages of the disease. CRCC has a propensity for vascular invasion and may be associated with distant metastasis at an early stage. Therefore, metastatic RCC at a distant location are most likely to be of CRCC origin than PRCC origin.