A 72-port (288 antennas) triangular-shaped massive multiple-input-multiple-output (mMIMO) antenna system is presented for fifth generation (5G) base stations. Each side of the antenna system consists of three layers with a total size of 44.4 × 29.6 × 0.1524 cm, and contains 24 ports. Each port (subarray) consists of 2 × 2 patches on the top layer, their feeding network with pre-calculated phases is on the bottom layer and the ground plane is in the middle one. Each port is fed in a way to tilt its beam direction with respect to others to achieve uncorrelated individual patterns. The antenna system is the first to support two operating modes: simultaneous individual port operation (i.e. 72-port MIMO) and mMIMO array operation (i.e. with beam switching). The measured bandwidth is 100 MHz that covers the band from 3.45 to 3.55 GHz. The measured gain of a single port equals to 9.41 dBi. The envelop correlation coefficient does not exceed 0.1198. A beamsteering method to steer the beam of each 24-port side to different locations in the space is presented and applied based on the non-uniform port patterns (unlike most conventional methods). Thirteen switched beams are obtained with centre angle coverage up to 34° in elevation with maximum gain of 19.5 dBi.