Cancer represents a significant global health challenge, with nearly 20 million new cases and over 9 million deaths annually. Early diagnosis is a key factor in improving survival rates, yet current diagnostic methods lack sensitivity, specificity, and accessibility. Glycosylation patterns of biomarkers offer a promising target for early detection of cancer and the development of personalized treatment strategies. The europium-doped nanoparticle-based glycovariant assay represents a novel approach that leverages time-resolved fluorescence for enhanced sensitivity and glycan moiety recognition for enhanced specificity. This review explores glycosylation changes in cancer, emphasizing their potential as diagnostic tools, with a particular focus on the europiumdoped nanoparticle-based glycovariant assay. The assay has demonstrated potential for identifying specific cancer-associated glycovariants in ovarian, prostate, breast, colorectal, and bladder cancers. The assay has the capacity to distinguish cancer-specific glycovariants from nonmalignant sources. However, further optimization and bigger sample cohorts are necessary to enhance the diagnostic utility of the assay.