title: Prognostic value of immunohistochemical markers in malignant thymic epithelial tumors.
abstract: BACKGROUND
  Thymic epithelial tumors (TET) are rare neoplasms with inconsistent treatment strategies. When researching for molecular pathways to find new therapies, the correlation between specific molecular markers and outcome has only rarely been investigated. The aim of this study was to investigate the correlation between survival, metastatic potential and invasiveness of aggressive subtypes of TET and immunohistochemical markers.
  
  
  METHODS
  Overall survival (OS), disease-free survival (DFS), progression-free survival (PFS) and metastasis-free survival (MFS) of patients with WHO type B2/B3 mixed type thymoma (MT), thymoma type B3 (B3) and thymic carcinoma (TC), undergoing surgery [1998-2013] were determined. Tumor specimens were stained using a tissue microarray (TMA) (CD117, CD5, p63, p40, p21, p27, p53, Bcl-2, Ki67, podoplanin, synaptophysin, PTEN and Pax8). Invasive behavior of primary tumors and the presence of extrathoracic metastases were assessed.
  
  
  RESULTS
  We found in 23 patients included into this study (four MT, ten B3, nine TC) that (I) p21 expression in the cytoplasm significantly correlated with a decrease of OS (P=0.016), PFS (P=0.034) and MFS (P=0.005); (II) MFS was significantly shorter when the combination of p21-low p27-low p53-high was present (P=0.029); and (III) nuclear p27 (P=0.042), Ki-67 (P=0.024) and podoplanin (P=0.05) expression correlated with the presence of extrathoracic metastases.
  
  
  CONCLUSIONS
  The main finding of this study is that cytoplasmic p21 expression negatively influences the outcome of malignant TETs and correlates with metastatic activity. Additionally, selected immunohistochemical markers correlate with the distant metastatic potential of TETs. These results may contribute to the stratification of diagnosis and improvement of treatment strategies for thymic malignancies.
authors.affiliation: Division of Thoracic Surgery, University Hospital Zurich, Zurich 8091, Switzerland.
authors.forename: Priska
authors.initials: P
authors.lastname: Leisibach
authors.affiliation: Division of Thoracic Surgery, University Hospital Zurich, Zurich 8091, Switzerland.
authors.forename: Didier
authors.initials: D
authors.lastname: Schneiter
authors.affiliation: Department of Pathology and Molecular Pathology, University Hospital Zurich, Zurich 8091, Switzerland.
authors.forename: Alex
authors.initials: A
authors.lastname: Soltermann
authors.affiliation: Division of Thoracic Surgery, University Hospital Zurich, Zurich 8091, Switzerland.
authors.forename: Yoshi
authors.initials: Y
authors.lastname: Yamada
authors.affiliation: Division of Thoracic Surgery, University Hospital Zurich, Zurich 8091, Switzerland.
authors.forename: Walter
authors.initials: W
authors.lastname: Weder
authors.affiliation: Division of Thoracic Surgery, University Hospital Zurich, Zurich 8091, Switzerland.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Jungraithmayr
keywords: Thymoma; immunohistochemistry; metastases; thymic carcinoma (TC)