Cyst-associated renal cell carcinoma: Clinicopathologic characteristics and evaluation of prognosis in 27 cases

Background: No consistent clinicopathologic characteristics of cyst‐associated renal cell carcinoma (CRCC) have previously been determined. Methods: In total, 768 patients with renal cell carcinoma (RCC) underwent radical or partial nephrectomy. Renal cell carcinoma was classified as CRCC in 27 of these patients (3.5%, subdivided into RCC originating in a cyst and cystic RCC), clear‐cell RCC in 662 patients (86.2%), chromophobe cell renal carcinoma in 36 patients (4.7%) and papillary RCC in 43 patients (5.6%) according to the criteria of the World Health Organization. Results: The pathologic stage and nuclear grade were usually lower in those with CRCC (low stage/low grade; 89%/96%) or chromophobe cell renal carcinoma (low stage/low grade; 89%/80%) than in those with clear‐cell RCC (low stage/low grade; 59%/65%) or papillary RCC (low stage/low grade; 53%/69%). Of the 27 CRCC patients, only 19 (70%) could be diagnosed through preoperative imaging studies. Patients with CRCC showed a favorable prognosis (survival rate: 95% at 1 year, 89.7% at 3 years and 84.4% thereafter) and, especially among the patients with RCC originating in a cyst, no cancer‐related death was observed. Comparing the survival among four types of RCC, a favorable outcome was observed in cases of CRCC or chromophobe cell renal carcinoma compared with clear‐cell RCC or papillary RCC (clear vs chromophobe: P = 0.002; chromophobe vs papillary: P = 0.019; clear vs cyst‐associated: P = 0.001; papillary vs cyst‐associated: P = 0.00079). Conclusions: In cases of CRCC, the disease was usually detected at lower stages and grades and therefore the prognosis was better than in cases of other types of RCC. Preoperative diagnosis of this disease was very difficult, especially in cases of RCC originating in a cyst.