A 56-year-old cancer patient developed a serious bloodstream infection caused by a rare yeast called Candida lambica despite taking antifungal medications. Doctors identified the infection using genetic sequencing and found that the organism was sensitive to a different antifungal drug called voriconazole. After switching medications and removing the patient’s central line, the infection cleared up. This case demonstrates the importance of accurately identifying fungal infections and testing which medications work best against them.