Results: CB/SSP agreement rates came out with 95 % for G1, 73 % for G2, and 56 % for G3. The PPVs of CB based HG were 56 % for G1, 61 % for G2 and 100 % for G3. The overgrading and undergrading rates on CB were 1 % and 37 %, respectively. Main causes for undergrading in CB were underestimated MA (40 %) and a combination of underestimated NP and MA (32 %). Conclusion: Whereas overgrading on CB is an exception, undergrading derives largely from underestimation of proliferation. Agreement of HG between CB and SSP ranges from almost perfect for G1, moderate for G2 to slight for G3 tumours.