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Sources of Funding: none

Introduction

Cystic clear cell renal cell carcinoma (ccRCC), defined as multilocular cystic renal neoplasms of low malignant potential or ccRCC with cystic change, comprises less than 5% of renal cortical neoplasms and has been associated with a favorable prognosis in small retrospective studies. Because studies are limited due to the rarity of this variant, we reviewed our experience with ccRCC and report on long term oncologic outcomes of cystic ccRCC.

Methods

We identified 3,865 patients treated with radical or partial nephrectomy for unilateral, sporadic ccRCC between 1970 and 2010. One urologic pathologist re-reviewed all pathologic slides, blinded to patient outcome. Cancer-specific survival (CSS) was estimated using the Kaplan-Meier method and compared between those with and without cystic ccRCC using log-rank tests.

Results

Overall, 158 of 3,865 (4%) patients had cystic ccRCC. Compared to patients with non-cystic ccRCC, patients with cystic ccRCC were younger (median 58 vs. 63 years, p<0.001), were more likely to have radiographic evidence of cystic structures (60% vs. 17%, p<0.001), were less likely to have distant metastases at surgery (0% vs. 14%, p<0.001), and had smaller tumors (median 3.0 vs. 6.0cm, p<0.001) that were less likely to contain coagulative tumor necrosis (1% vs. 29%, p<0.001) or sarcomatoid differentiation (0% vs. 5%, p=0.006).With a median follow-up for survivors of 10.5 years (IQR 7.3-14.9), 63 patients with cystic ccRCC died at a median of 7.7 years after surgery (IQR 3.8-11.9). However, only one patient died from RCC after developing metastases 22 years after the initial surgery. CSS rates at 25 years following surgery were significantly better for cystic ccRCC compared to non-cystic ccRCC (88% vs. 52%, p<0.001) (Figure 1), even among the subset of pT1, pNX/0, M0 patients (100% vs. 83%, p=0.001).

Conclusions

In a large cohort of ccRCC patients with pathologic re-review and long-term follow-up, our results suggest that cystic ccRCC is both uncommon and associated with a very favorable prognosis.

Funding

none