(a, b) Optical micrographs of patient 4's biopsy at two different magnifications [(a) 10× and (b) 100×] revealing the presence of micrometre-size blue pigments PB15. (c) Corresponding Raman spectra collected at the excitation wavelength λexc = 785 nm and 532 nm (top and bottom spectra, respectively, objective 100×, numerical aperture = 0.9). The presence of anatase is revealed using a 532 nm Raman probe as shown in the chemical mapping (red pixels, intensity of the 143 cm−1 band) overlapped with the 100× micrograph. Top spectrum is baseline corrected. Reference spectra are also given as comparison: PB15 C.I. 74160, Polycyclic pigment, Phthalocyanine from the Soprano spectral library, anatase (TiO2) downloaded from the RRUFF spectral library (ID R110109, 780 nm).