We present a case study of a patient with aggressive B-cell lymphoma and demonstrate the benefits of utilizing modern laboratory methods in addition to standard examinations. By integrating the results of various tests, we can refine the diagnosis and monitor the progression of the disease more accurately. Using the NGS panel LYNX (PMID: 34082072), we compared genomic aberrations found in different biological materials such as bone marrow, plasma, and cerebrospinal fluid. Unfortunately, the initial histological material was not available. However, consolidating the results of molecular examinations allowed us to classify this case as "DLBCL/high-grade B-cell lymphoma with MYC and BCL2 rearrangement." Combining comprehensive testing with less invasive analysis of liquid biopsies enables individual tumor genotyping and detection of lymphoma progression into the CNS.