Background/Objectives: Chronic lymphocytic leukemia (CLL) is a hematologic malignancy characterized by uncontrolled accumulation of B lymphocytes. A key feature of CLL is the presence of genetic aberrations, particularly alterations of chromosome 17, such as deletion of 17q and/or mutations in theTP53gene. Since these abnormalities are highly relevant for therapeutic decision-making, assessment ofTP53mutational status is strongly recommended in routine diagnostics. This study aimed to evaluate the reliability ofTP53sequencing results depending on the type of DNA sample analyzed. Methods: DNA was isolated from two different sample types of the same patient: mononuclear cells (CLL1) and purified CD19+ cells (CLL2). The entire coding region ofTP53(exons 2–11), including splice sites (+/− 10 bp), was analyzed using capture-based next-generation sequencing (NGS). Reads were aligned to the GRCh37/hg19 reference genome, and variants were interpreted using DRAGEN Enrichment (Illumina) and Franklin (QIAGEN). Results: In sample CLL1, the NM_000546.6:c.626_627del mutation (Tier I) was identified with a variant allele frequency (VAF) of 57.06%. The same mutation was confirmed in CLL2, but with a higher VAF of 94.78%. Importantly, an additional Tier I mutation (NM_000546.6:c.825_826del) was detected exclusively in CLL2 at a VAF of 1.59%. Both findings met the required sequencing depth as well as coverage per sample, confirming their validity. Conclusions: The study demonstrates that inadequate starting material for DNA isolation may mask low-frequencyTP53mutations, resulting in false-negative results. Accurate detection requires ensuring sufficient CD19+ cell content, which is critical for reliable diagnostics and supports personalized treatment approaches in CLL.
**背景/目的：** 慢性淋巴细胞白血病（CLL）是一种以B淋巴细胞不受控制地积聚为特征的血液系统恶性肿瘤。CLL的一个关键特征是存在遗传学异常，尤其是17号染色体的改变，例如17q缺失和/或TP53基因突变。由于这些异常与治疗决策高度相关，强烈建议在常规诊断中评估TP53突变状态。本研究旨在评估TP53测序结果的可靠性是否取决于所分析的DNA样本类型。 **方法：** 从同一患者的两类不同样本中分离DNA：单个核细胞（CLL1）和纯化的CD19+细胞（CLL2）。使用基于捕获的新一代测序技术（NGS）分析了TP53的整个编码区（外显子2-11），包括剪接位点（+/- 10 bp）。测序读段与GRCh37/hg19参考基因组进行比对，并使用DRAGEN Enrichment（Illumina）和Franklin（QIAGEN）对变异进行解读。 **结果：** 在样本CLL1中，检测到NM_000546.6:c.626_627del突变（Tier I），其变异等位基因频率（VAF）为57.06%。在CLL2样本中确认了相同的突变，但VAF更高，为94.78%。重要的是，仅在CLL2样本中额外检测到一个Tier I突变（NM_000546.6:c.825_826del），其VAF为1.59%。两项发现均满足所需的测序深度和样本覆盖度，证实了其有效性。 **结论：** 本研究表明，用于DNA分离的起始材料不充分可能会掩盖低频TP53突变，导致假阴性结果。准确的检测需要确保足够的CD19+细胞含量，这对于可靠的诊断至关重要，并支持CLL的个体化治疗策略。
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