papillary renal cell carcinoma

In 1997, two types of papillary renal cell carcinoma (pRCC) with a distinctively different prognosis and outcome were described [1]. It is remarkable that this distinction has often not been made in studies evaluating the outcome of pRCC, despite the observations of two very different clinical subgroups as recently as 2012 [2]. Kim et al. made an effort to analyze the prognostic impact of pRCC type on venous tumour thrombi, adding important data to our understanding of this second most common RCC subtype. Generally, type I is associated with a lower grade and stage and a better prognosis, whereas type II is more common in younger patients and frequently associated with advanced stage and poorer outcome [1]. Although the prevalence of type I pRCC is reported to be higher than type II, this may be biased by pathology studies primarily including tissue obtained at curative nephrectomy for lower stages. Interestingly, no type I thrombi were observed in the present study. In metastatic pRCC, a report on RCC subtype and cytokine therapy found 87.5% of pRCC to be of type II [3]. This strongly suggests that type II progresses more commonly than type I. This appears to be reflected in the study conducted by Kim et al. in which all pRCC tumour thrombi were of type II. Despite small numbers and concerns of multivariate analyses in these settings, the association is compelling. Kim et al. provide information for a risk-adapted follow-up of these patients. This makes sense because drugs are becoming available that target pathways involved in pRCC, such as the mesenchymal-epithelial transition factor [4] pathway in type I and potentially MYC and fumarate hydratase in type II. Targeted therapy trials are ongoing, focusing not only on types of pRCC, but also on mutation activation status, which may eventually lead to improved outcomes for pRCC [5].


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