Excess of massive log(M_⋆/M_⊙)≳10.5 galaxies around the MQN01 QSO. Left panel: cumulative stellar mass function of the MQN01 spectroscopic sample in proximity to the QSO (black stars) compared to the control-field sample (orange diamonds) and the expectations for blank fields from the COSMOS survey (3.0 < z < 3.5, Weaver et al. 2023, gray). Right panel: same as the left panel, but normalized to the value of the cumulative mass function at M_⋆ = 10^9.8 M_⊙, corresponding to the 90% completeness limit of the MQN01 spectroscopic sample.