Protein p62 common in invaginations in benign meningiomas--a possible predictor of malignancy

It is known that p62 is a cytosolic conserved protein that binds non-covalently to ubiquitin. Expression of p62 has been seen in inclusions in neoplasias like hepatocellular and breast carcinomas but also in neuronal inclusions of degenerative brain disorders. Dysfunction of ubiquitin system leads to presence of p53 in cells suggested to be a predictor of future recurrence of meningioma.

The study material included 45 benign meningiomas of postmenopausal women operated in Kuopio University Hospital between 1994 and 2002.

Patterns of p62 immunopositivity in meningiomas was evaluated and the results were correlated to clinical and histological parameters.

Constant p62 labeling in at least each field measuring 1 mm in diameter was detected consisting of 5 different patterns. The most common labeling was seen in nuclear invaginations either as grains or homogenous labeling, followed by Marinesco like nuclear inclusions or rode like inclusions outside the invagination. In some cases cytoplasmic granular staining was seen. No correlation between different p62 patterns or extent of p62 expression, histological subtypes or proliferation marker Ki-67 was noted.

Our results indicate that in the benign not recurrent meningiomas, signs of functioning proteosomal system, can be detected using the p62 labeling. The function of proteosomal system in malignant and specifically invasive meningiomas needs to be further elucidated.