Die Expression von MSR1 ist mit der Infiltration durch M2-Makrophagenin in Vestibularisschwannomen assoziiert sowie mit stärkerer Proliferation.

The concept of tumor associated macrophages has been applied to vestibular schwannomas, based on increasing evidence of the impact of inflammatory regulations during tumor progression. The macrophage scavenging receptor 1 (MSR1) has been linked to several pathological processes including an unfavorable prognosis in different cancers. It has become established as a tissue marker for tumor associated macrophages. While inflammation has gained increasing interest in vestibular schwannomas, the expression and distribution of MSR1 has not yet been described in vestibular schwannomas.

We analyzed the immunohistochemical expression of MSR1 in 1272 vestibular schwannoma tissue samples. The distribution and correlation with clinical factors such as age, gender, tumor size, NF2, prior radiation, recurrent tumor status, the proliferation marker MIB1 and volumetric tumor growth. MSR1 expression was assessed using a semiquantitative score. CD163 was applied for the detection of M2 macrophages and samples were semiquantitatively scored. MIB1 expression was measured with the help of a digital quantification plugin.

MSR1 expression showed marked differences among vestibular schwannoma samples and a higher expression was significantly associated with a more extensive infiltration with M2 macrophages (p<0.0001). There was no difference of MSR1 expression regarding age, gender, prior radiotherapy or recurrent tumor status. NF2 associated tumors showed a lower MSR1 expression (p=0.0005). No association of MSR1 expression with volumetric tumor growth was observed, but with MIB1 expression (p<0.0001).

MSR1 expression identifies M2 macrophages in vestibular schwannomas and is associated with increased proliferation expressed by MIB1.