Morphological and genetic heterogeneity of synchronous multifocal lung adenocarcinoma in a Chinese cohort

Background Synchronous multifocal lung cancer (SMLC) is diagnosed with increasing frequency in clinical practice globally. Due to innate variation in clinical management and outcome, it is vital to properly distinguish between synchronous multifocal primary lung cancer (SMPLC) and intrapulmonary metastasis (IM). The pathologic features and principal classification criteria of multifocal lung cancer remain unclear. Our objective was to evaluate the diagnostic value of histological morphologic features and driver gene mutations in SMLC classification. Methods We collected a unique cohort of Chinese patients with SMLC, and fully explored the morphologic, immunohistochemical, and molecular features of the disease. Twenty-one SMLC patients with a total of 50 tumours were included in our study. The pathological features that were presented by these patients were analysed, including the tumours location, tumours size, pathological types, predominant pattern of adenocarcinoma, and immunohistochemical staining. We conducted molecular testing of nine driver oncogenes that are associated with lung cancer, namely, EGER, KRAS, BRAF, NRAS, ALK, ROS1, RET, HER2, and PIK3CA. Results According to the Martini-Melamed classification and refined standard, 8 and 17 patients, respectively, were considered to have SMPLCs. Gene mutations were identified in 18 tumours (36%). Twelve patients had different gene mutations. Conclusions We demonstrate that conventional morphological assessment is not sufficient to clearly establish the clonal relationship of SMPLCs. Instead, the evaluation of histological subtypes, including nonmucinous adherent components, is required. Multiplex genotypic analysis may also prove to be a useful additional tool.