ALCAM (CD166) expression as novel prognostic biomarker for pancreatic neuroendocrine tumor patients. 
Activated leukocyte cell adhesion molecule (ALCAM, CD166) is a cell membrane protein that is aberrantly expressed in different tumors, including pancreatic neuroendocrine tumors (PNET).  The aim of this study was to determine the expression of ALCAM in PNET to learn more about the prevalence and clinical significance of ALCAM expression in PNET.  Primary tumors (n = 38) and corresponding lymph node (n = 5) and liver metastases (n = 9) of patients with PNET, treated at the University Medical Center Hamburg-Eppendorf between 1993 and 2006, were analyzed via ALCAM immunohistochemistry in a tissue microarray format.  The results were correlated with clinical and histopathologic data, including the WHO classification of PNET.  The majority of primary (74%) and secondary (50%) lesions of PNET showed strong ALCAM expression.  Immunohistochemistry of primary tumors revealed an association between high ALCAM expression and the hormone production status of the tumor (P = 0.037), and an inverse correlation with metastasis status (P = 0.041) and tumor size (cut off level 2 cm, P = 0.013).  Elevated ALCAM expression was a significant positive prognostic factor for recurrence-free (P = 0.002) and disease-specific survival (P = 0.009) in Kaplan-Meier survival analysis (log rank test).  ALCAM is abundantly expressed in PNET and decreased expression is significantly associated with poor prognosis.  ALCAM may be a potential marker for risk prediction in patients diagnosed with PNET.  Further studies with larger patient collectives are required to validate the results of this study and investigate the functional role of ALCAM in PNET.