Primary Lung Cancer Subtypes: How Does Chest CT Scan Help to Differentiate them?

Background: Lung cancer has wide variety of clinical presentations and different imaging features relating its subtypes. This study is focused on the role of CT scan in differentiating primary lung cancer subtypes including adenocarcinoma, squamous cell carcinoma and small cell carcinoma. Materials and Methods: This retrospective study is conducted on 55 pathologically diagnosed primary lung cancer patients. Several CT features including lung mass and pleural effusion and parenchymal nodule characteristics, mediastinal and hilar involvement, pericardial effusion and thickening, chest wall invasion, reticulation, superior vena cava (SVC) syndrome and encasement of main bronchus were checked. Results: We enrolled 55 primary lung cancer patients including 29 adenocarcinomas, 19 squamous cell carcinomas and 7 small cell carcinomas, 36 males and 19 females with mean age of 60.3 years. Most common CT features of primary lung cancer were lung mass (94.5%) particularly located in hilum (51.9%) and irregular bordered (55.8%). Other prevalent findings included parenchymal nodules (60%), pleural effusion (41.8%), mediastinal adenopathy (47.3%), hilar adenopathy (42.9%), mediastinal invasion (43.6%) and reticulation (56.4%). Hilar adenopathy (47.4%), reticulation (48.3%) and parenchymal nodule (62.1%) in adenocarcinoma; hilar mass (57.9%) and parenchymal nodule (68.4%) in squamouos cell carcinoma; hilar and mediastinal involvement in small cell carcinoma were the most frequent findings. Conclusion: Comparing three subtypes, we found squamous cell and adenocarcinoma more similar regarding CT images parenchymal nodules, mass calcification and cavitation were more frequently seen in them compared to small cell lung cancer whereas hilar involvement, mediastinal involvement, irregular bordered mass and encasement of main bronchus were more prevalent in small cell carcinoma.