Fig. 3
Comparison of traditional tissue biopsy and “liquid biopsy”. a: Diagnosis and anti-tumor therapeutic decisions are limited by temporal and intratumoral heterogeneity using traditional tissue biopsies. A mass of tumor tissue consists of several blocks of tumor cell subtypes, while tumors simultaneously at different stages of development (e.g., primary tumors and metastases) can also carry different features. Therefore, samples obtained from tissue biopsy may not provide comprehensive information for diagnosis and therapeutic decisions. b: Analysis of ctDNA can present profiles of point mutations, methylation, copy number variations, and histone acetylation, among others, thus providing relatively comprehensive information about the tumor of interest