Thanks to our MALDI-TOF lipid analyses, we detected various Pls species (such as PlsE, PlsS, PlsA, and PlsC) in both melanoma cell lines; noteworthy is the significant decreased content of PlsC O-32:0 and PlsC P-34:0/O-34:1 species in the highly metastatic cells. The gene discussed is CTSC; the disease is melanoma.