A case of bilateral synchronous double primary lung cancer secondary to bladder cancer: From the next‐generation sequencing prospect

One year following bladder cancer surgery, a 65‐year‐old man had computed tomography (CT) that revealed bilateral pulmonary nodules. Pulmonary wedge resections were performed after the nodules were found to grow in follow‐up. Unusually, we found that these two lesions were not homologous, nor were they metastases from prior bladder cancer, and therefore, synchronous double primary lung cancer (sDPLC) was diagnosed. The immunohistochemical findings excluded the possibility of bladder cancer metastasis, but could not determine whether they were from the same source. Next generation sequencing (NGS) supported the diagnosis sDPLC because they amply demonstrated the two sources’ distinct origins. Finally, after discussion with pathologists, this patient was diagnosed as small cell lung carcinoma (SCLC) and received postoperative EP chemotherapy. We also documented a few rather uncommon alterations that might serve as a foundation for further investigation. This case suggests that in addition to immunohistochemical, NGS is also helpful to clarify the etiology and refine the pathological classification of tumors, which has guiding significance for the establishment of precise diagnosis and optimal treatment.