Implementing amplicon-based next generation sequencing in the diagnosis of small cell lung carcinoma metastases

• SCLC metastases harbored synchronous mutations in TP53 and RB1.
• CREBBP and EP300 mutations occurred non-synchronously in SCLC metastases.
• SCLC lymph node metastases frequently harbored a collapsed keratin cytoskeleton.
• Tracheal SCLC metastases may represent metastases per continuitatem.

Small cell lung carcinoma (SCLC) is the most aggressive entity of lung cancer. Rapid cancer progression and early formation of systemic metastases drive the deadly outcome of SCLC. Recent advances in identifying oncogenes by cancer whole genome sequencing improved the understanding of SCLC carcinogenesis. However, tumor material is often limited in the clinic. Thus, it is a compulsive issue to improve SCLC diagnostics by combining established immunohistochemistry and next generation sequencing.We implemented amplicon-based next generation deep sequencing in our routine diagnostics pipeline to analyze RB1, TP53, EP300 and CREBBP, frequently mutated in SCLC. Thereby, our pipeline combined routine SCLC histology and identification of somatic mutations. We comprehensively analyzed fifty randomly collected SCLC metastases isolated from trachea and lymph nodes in comparison to specimens derived from primary SCLC.SCLC lymph node metastases showed enhanced proliferation and frequently a collapsed keratin cytoskeleton compared to SCLC metastases isolated from trachea. We identified characteristic synchronous mutations in RB1 and TP53 and non-synchronous CREBBP and EP300 mutations.Our data showed the benefit of implementing deep sequencing into routine diagnostics. We here identify oncogenic drivers and simultaneously gain further insights into SCLC tumor biology.