  Accretion disks are an essential component in the paradigm of the formation
of low-mass stars. Recent observations further identify disks surrounding
low-mass pre-main-sequence stars perturbed by flybys. Whether disks around more
massive stars evolve in a similar manner becomes an urgent question. We report
the discovery of a Keplerian disk of a few solar masses surrounding a 32
solar-mass protostar in the Sagittarius C cloud around the Galactic Center. The
disk is gravitationally stable with two embedded spirals. A combined analysis
of analytical solutions and numerical simulations demonstrates that the most
likely scenario to form the spirals is through external perturbations induced
by a close flyby, and one such perturber with the expected parameters is
identified. The massive, early O-type star embedded in this disk forms in a
similar manner with respect to low-mass stars, in the sense of not only
disk-mediated accretion, but also flyby-impacted disk evolution.
