Chronic sun-damaged (CSD) melanoma represents 10%-20% of cutaneous melanomas and is characterized by infrequent BRAF V600E mutations and high mutational load. However, the order of genetic events or the extent of intra-tumor heterogeneity (ITH) in CSDhigh melanoma is still unknown. Ultra-deep targeted sequencing of 40 cancer-associated genes was performed in 72 in situ or invasive CMM, including 23 CSDhigh cases. In addition, we performed whole exome and RNA sequencing on multiple regions of primary tumor and multiple in-transit metastases from one CSDhigh melanoma patient. We found no significant difference in mutation frequency in melanoma-related genes or in mutational load between in situ and invasive CSDhigh lesions, while this difference was observed in CSDlow lesions. In addition, increased frequency of BRAF V600K, NF1, and TP53 mutations (p < .01, Fisher's exact test) was found in CSDhigh melanomas. Sequencing of multiple specimens from one CSDhigh patient revealed strikingly limited ITH with >95% shared mutations. Our results provide evidence that CSDhigh and CSDlow melanomas are distinct molecular entities that progress via different genetic routes.

中文翻译：

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慢性晒黑性黑色素瘤的肿瘤遗传异质性分析。

慢性晒黑（CSD）黑色素瘤占皮肤黑色素瘤的10％-20％，其特征是BRAF V600E突变少且突变负荷高。然而，尚不清楚CSD高黑素瘤中遗传事件的顺序或肿瘤内异质性（ITH）的程度。在72个原位或侵入性CMM中（包括23个CSDhigh病例）对40个与癌症相关的基因进行了超深度靶向测序。此外，我们对一名CSD高黑素瘤患者的原发肿瘤的多个区域和多个转移中的转移进行了完整的外显子组和RNA测序。我们发现黑色素瘤相关基因的突变频率或原位与浸润性CSDhigh病变之间的突变负荷无显着差异，而在CSDlow病变中观察到此差异。此外，BRAF V600K，NF1，在CSD高型黑色素瘤中发现了TP53和TP53突变（p <0.01，Fisher精确检验）。一名CSD高患者的多份标本测序显示，惊人的有限ITH具有超过95％的共享突变。我们的结果提供了证据，表明CSDhigh和CSDlow黑色素瘤是通过不同遗传途径发展的截然不同的分子实体。