Subtyping of Non-Small Cell Lung Carcinoma in Fine Needle Aspiration Specimens: A Study of 252 Patients with Surgical Correlations

Objective: Fine-needle aspiration (FNA) cytology performed by either transthoracic or transbronchial procedures is an important approach to obtain tumor tissue for histological diagnosis. We investigated the accuracy of FNA in differentiating NSCLCs of adenocarcinoma from squamous cell carcinoma histological types to correlate cytological findings with histological features and immunohistochemistry confirmation in some cases.
Methods: From 2010 to 2015, a total of 635 transbronchial needle aspirations or transthoracic needle aspirations were performed. 332 cases were diagnosed as NSCLC, with or without an indication of a specific subtype, while 303 cases were not diagnosed as NSCLC. Out of 332 cases diagnosed as NSCLC, 252 had a histological follow-up. Subsequently, histological samples included 161 surgical resections and 91 biopsies. In cases with histopathological diagnosis accompanied by FNA cytology, an immunohistochemical study was carried out and the diagnostic results of the two methods were compared to each other.
Results: The specific subtype of NSCLC was provided in 217 cases (86%) based on cytomorphology which included 115 adenocarcinomas (46%) and 102 squamous cell carcinomas (40%). The diagnosis NSCLC-NOS by FNA was set in 35 cases. At histology, 251 cases (99.6%) were sub-classified: 122 adenocarcinomas (48%), 104 squamous cell carcinomas (41%), 11 large cell carcinomas (4%), and 14 adenosquamous carcinomas (6%). Agreement between cytological and histological typing was found in 181 of 197 cases (92%) (K=0.837; p<0.001).
Conclusion: Our study proved that most NSCLC can be sub-classified as adenocarcinoma or squamous cell carcinoma by FNA through cytomorphology and the application of immunocytochemistry.