Although the two major subtypes of papillary renal cell carcinoma (PRCC) differ on a variety of measures of aggressiveness, subtype is not independently prognostic, according to a retrospective cohort study conducted by the German Network of Kidney Cancer.
Investigators led by Iris Polifka, an intern at the Institute of Pathology at the University Hospital Erlangen (Germany), characterized 376 renal tumors initially diagnosed as PRCC. They reviewed histologic features and performed immunohistochemical staining for a range of markers.
Main study results, which were reported in, showed that 65.4% of the tumors were PRCC subtype 1 and 34.6% were PRCC subtype 2. The former more commonly had foamy macrophages and expressed cytokeratin 7, whereas the latter more commonly had abundant cytoplasm, expressed E-cadherin and p53, and had high MIB1 expression (staining of more than 15% of cells), which indicated a high proliferation rate (P less than .05 for each). The latter also had higher stage and higher grade.
Univariate analysis in the entire study cohort showed that racemase expression and cytokeratin 7 expression were favorable prognostic factors for overall survival, whereas presence of abundant cytoplasm and psammoma bodies, high MIB1 expression, and PRCC subtype 2 were unfavorable prognostic factors.
However, in multivariate analysis, only four factors were independent predictors of death: high tumor MIB1 expression (hazard ratio, 2.465; P = .033), higher T stage (P = .036), metastases (HR, 4.334; P = .011), and age older than the median of 63 years at surgery (HR, 2.384; P = .005). Notably, tumor subtype did not independently predict this outcome.
“[T]he better [overall survival] in PRCC1 is mainly a reflection of its encapsulated nature associated with lower TNM stage … while enhanced proliferation might add to the aggressive nature of high grade and high stage tumors independently from PRCC subtype,” the investigators propose.
“PRCC subtype on its own is not suitable for estimating survival. More data focusing on PRCC tumor biology is needed to define prognostic subgroups, especially in PRCC2,” they conclude.
The investigators disclosed that they had no relevant conflicts of interest. The study did not receive any specific funding.
SOURCE: Polifka I et al. Hum Pathol. 2018 Aug 16. .