NGAL immunohistochemical expression in brain primary and metastatic tumors

A significant association has been recently shown between the expression of neutrophil gelatinase-associated lipocalin (NGAL) in tumors and its urinary levels. Thus NGAL urinary detection has been proposed as a method for the early diagnosis of brain tumors. In view of this, the objective of this study was to investigate whether NGAL expression differs according to brain tumor type or in primary vs. metastatic brain neolasias. 42 surgically resected formalin fixed and paraffin embedded neoplasias, including 15 cases of brain metastasis and 27 cases of primary central nervous system (CNS) tumors (11 meningiomas; 1 pilocytic astrocytoma, 2 diffuse astrocytomas, 2 oligoastrocytomas, 2 oligodendrogliomas, 1 anaplastic oligoastrocytoma, 7 glioblastomas, 1 ependymoma) were submitted to the immunohistochemical procedure. Sections were incubated overnight with the primary antibody against NGAL. NGAL staining was found in all the analyzed glioblastomas and in the anaplastic oligoastrocytoma. No NGAL immuno-expression was evidenced in all the other cases. A statistically significant correlation was demonstrated between NGAL presence and high proliferation index in the primary tumors. In conclusion, our findings suggest that NGAL expression is restricted to high grade gliomas among primary brain tumors, and that brain metastases do not express this protein. Considering the correlation between NGAL expression in tumors and its urinary levels, if our observations will be further validated, NGAL urinary detection might be used as an additional tool in the pre-surgical definition of brain lesions involving difficult differential diagnosis.