Chromophobe renal cell carcinoma in Iceland: an epidemiological and clinicopathological study

Numerous studies have suggested that the rare chromophobe renal cell carcinoma (CRCC) has a more favourable prognosis than the other more common subtypes of RCC, clear cell RCC (CCRCC) and papillary RCC (PRCC). These studies have, however, usually involved selected patient cohorts and not whole populations. This study compared CRCC patients with patients with the other two major histological subtypes and established a population-based age-standardized incidence rate (ASR).

Of 828 histopathologically confirmed RCCs diagnosed between 1971 and 2005 in Iceland, 15 CRCC cases were identified. Histological material was reviewed, the TNM system was used for staging and cancer-specific survival was estimated. Univariate and multivariate analysis was used to compare CRCC to both CCRCC (n = 740) and PRCC (n = 66). Mean follow-up was 6.7 years.

CRCC accounted for 1.8% of RCCs, the ASR being 0.17/100,000 per year. Compared to other subtypes, CRCC was detected incidentally less often (7% vs 29%, p = 0.02), but was more often diagnosed at lower stages (73% vs 45% at stage I + II, p < 0.001). One patient had synchronous metastasis and another developed recurrent CRCC; both died of CRCC. Five-year survival for CRCC, CCRCC and PRCC was 86%, 59% and 50%, respectively (p = 0.004). After correcting for TNM stage (odds ratio 1.98), multivariate analysis did not indicate that CRCC subtype was an independent predictive factor for survival.

CRCC is a rare neoplasm with an ASR of 0.17/100,000 per year. These tumours often present with symptoms despite being at lower stages than the other RCC subtypes. The more favourable survival of the CRCC subtype appears to be explained by these tumours being diagnosed at low stages. These findings may suggest that CRCC has a different biological behaviour.