Breast cancer (BC) is the most common tumor worldwide
and requires
crucial molecular typing for treatment and prognosis assessment. Currently,
approaches like pathological staining, immunohistochemistry (IHC),
and immunofluorescence (IF) face limitations due to the low signal-to-background
ratio (SBR) and high tumor heterogeneity, resulting in a high misdiagnosis
rate. Fluorescent assay in the second near-infrared region (NIR-II,
1000–1700 nm) exhibits ultrahigh SBR owing to diminished scattering
and tissue autofluorescence. Here, we present a NIR-II strategy for
accurate BC molecular typing and three-dimensional (3D) visualization
based on the atomically precise fluorescent Au24Pr1 clusters. Single-atom Pr doping results in 3.9-fold fluorescence
enhancement and long-term photostability. The Au24Pr1 clusters possess high fluorescence centered at ∼1100
nm and the SBR on pathological section diagnosis was 4 times higher
than that of NIR-I imaging. This enables high spatial resolution 3D
visualization of biopsy specimens, which can surmount tissue heterogeneity
for clinical diagnosis of BC.