Cystic renal cell carcinomas: do they grow, metastasize, or recur?

The purpose of this study is to evaluate the interval growth, tumor recurrence, and metastatic disease occurrence of cystic renal cell carcinoma (RCC). Pre-and posttreatment imaging of 47 histologically proven cystic RCCs, with at least 6 months of pretreatment imaging monitoring or at least 2 years of posttreatment imaging follow-up, or both, was retrospectively reviewed. Tumor morphologic features, preoperative growth, histologic typing and grading, and the incidence of tumor recurrence or metastasis were evaluated. Growth rate of tumors were compared among various histologic subtypes and Fuhrman grades. Of 47 tumors, 27 (57.5%) were clear cell RCCs, 12 (25.5%) were multilocular RCCs, and eight (17%) were papillary cystic RCCs. Overall, 26 (55.3%) tumors were graded as Fuhrman grade 2, 17 (36.1%) were Fuhrman grade 1, and one tumor was Fuhrman grade 3. Of the 26 tumors with a minimum of 6 months of pretreatment imaging monitoring, 19 (73%) did not show a significant increase in tumor size. The differences in mean growth among the Fuhrman grades and different subtypes were not statistically significant. The average duration of posttreatment follow-up was 51 months. There were no local recurrences among the 43 patients who underwent posttreatment imaging, except for one patient who had metastasis at preoperative clinical presentation. Cystic RCCs exhibit slow indolent growth, if any, and show no significant metastatic or recurrence potential, with excellent clinical outcomes. We raise the need for revisiting current imaging protocols that may involve frequent pre-and posttreatment imaging in cystic RCCs.