We study symmetry protected features in the quasiparticle interference (QPI) pattern of 2D systems with mirror symmetries and time-reversal symmetry, around a single static point impurity. We show that, in the Fourier transformed local density of states (FT-LDOS), ρ(,ω), while the position of high intensity peaks generically depends on the geometric features of the iso-energy contour at energy ω, the absence of certain peaks is guaranteed by the opposite mirror eigenvalues of the two Bloch

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... s that are (i) on the mirror symmetric lines in the Brillouin zone (BZ) and (ii) separated by scattering vector . We apply the general result to the QPI on the <001 >-surface of topological crystalline insulator Pb_1-xSn_xTe and predict all vanishing peaks in ρ(,ω). The model-independent analysis is supported by numerical calculations using an effective four-band model derived from symmetry analysis.