Dynamic transition of molecular subtypes in relapsed small cell lung cancer treated with multimodal therapy: A case report

Several transcription factors in small cell lung cancer (SCLC), including achaete‐scute homolog 1 (ASCL1) and neurogenic differentiation factor 1 (NEUROD1), contribute to rapid tumor growth and early metastatic dissemination. Recent studies suggested that these molecular subtypes represent neuroendocrine differentiation in dynamic SCLC evolution. In the present case, a 62‐year‐old man was diagnosed with limited disease SCLC originating from the right upper lobe. Biopsy specimens were positive for ASCL1 but negative for NEUROD1. Six months after concurrent chemoradiotherapy and prophylactic cranial irradiation, the primary tumor had regrown and salvage surgery was performed. The pathological diagnosis was recurred SCLC, and postoperative histopathology was positive for both ASCL1 and NEUROD1. The patient was subsequently followed up; however, he had multiple bone metastases 9 months after surgery. It was speculated that the shift to NEUROD1‐high expression in tumor cells surviving concurrent chemoradiation therapy may be related to the poor outcome after combined modality treatment.