Immunohistochemical Expression of p27 Kip1 , p57 Kip2 , Cyclin D1, Nestin, and Ki-67 in Ependymoma.

p27 and p57 are tumor suppressors that are dysregulated in many cancers. We investigated the immunohistochemical expression of p27 and p57 in ependymoma, with a secondary emphasis on cyclin D1, nestin, and Ki-67. Sixty-five patients diagnosed with ependymoma were included. Clinical and tumoral data were retrieved, and the expression of p27, p57, cyclin D1, nestin, and Ki-67 was measured. Pearson's χ 2 test was used to measure associations and the Kaplan-Meier method was used for survival analysis. p27 underexpression was significantly associated with pseudopalisading necrosis in tumors with foci of necrosis ( p = 0.004). Cyclin D1 overexpression was associated with intracranial ( p = 0.044), recurrent ( p = 0.022) and grade 3 tumors ( p = 0.016); nestin overexpression was associated with supratentorial ( p = 0.025), mitotically active ( p < 0.001), and grade 3 tumors ( p = 0.004); Ki-67 overexpression was associated with supratentorial ( p = 0.044) and grade 3 tumors ( p < 0.001) and the 3 main features of anaplasia. None of the markers were intercorrelated or predictive of overall survival. In conclusion, p27 underexpression in tumors with foci of necrosis signals a pseudopalisading pattern. Cyclin D1, nestin, and Ki-67 are useful markers in ependymoma, but evidence-based cutoff values are required to standardize this interpretation.