Molecular genetic characterization reveals linear tumor evolution in a pulmonary sarcomatoid carcinomas patient with a novel PHF20-NTRK1 fusion: a case report

BACKGROUND: Pulmonary sarcomatoid carcinoma (SC) consists of both carcinomatous and sarcomatous tumors with high degree of malignancy, rapid progression, and poor prognosis. However, little is known regarding how pulmonary SC develops and progresses. CASE PRESENTATION: A 66-year-old male was initially diagnosed with stage IIIa lung cancer containing both adenocarcinoma (ADC) and SC. Adjuvant chemotherapy was administrated post-surgery, however, recurrence with SC only soon followed. Mutation profiling of the patient’s microdissected ADC and SC components of the primary lesion and recurrent tumor was performed by targeted next-generation sequencing (NGS) of 416 cancer-relevant genes. Our data showed that primary SC/ADC and the recurrent SC shared multiple gene mutations including EGFR, NF1, TP53, CDKN2B, and SMARCA4, while both primary and recurrent SCs had a unique TP53 exon 4 splicing mutation frequently observed in sarcoma. Interestingly, a novel PHF20-NTRK1 fusion was acquired in the recurrent SC, which may be a potential driver for SC recurrence. CONCLUSIONS: The molecular genetic characteristics of tumor tissues at different stages reveals a linear tumor evolution model in this case, and support that the primary SC derived from the original lung ADC during the evolution of the tumor. We also identified a novel PHF20-NTRK1 fusion, which may contribute to the disease recurrence, and that can be potentially targeted with NTRK1 inhibitors for treatment.