Bone hemangioendothelioma: an immunohistochemical study related to histological malignancy and proliferative activity (NORs).

Aims and Background: Forty-four bone hemangioendotheliomas (HEs) of different histological grades were studied to evaluate the expression and distribution of laminin, type IV collagen, cathepsin G and cathepsin D in cell differentiation and malignancy.
Results: In poorly-differentiated HEs the discontinuous distribution of laminin and type IV collagen around angioblastic cords, tubes and cavities revealed an irregular and disorganized basement membrane (BM) architecture corresponding to an increased cell proliferation and secretion of cathepsin D and cathepsin G by tumor cells.
Conclusions: The mean nucleolar organizer region (NOR) area, as a measure of cell proliferation, was significantly higher in grade 4 malignancies than in lower grades, revealing novel prognostic parameters.