Chest X-ray of a 63-year-old smoker shows a hilar mass, mediastinal widening, and cavitation. The most likely diagnosis is

• A. Squamous cell carcinoma
• B. Adenocarcinoma
• C. Mesothelioma
• D. Large cell tumor

Answer: (A)

Central, hilar lung cancers in smokers often show cavitation because the tumor tends to outgrow its blood supply, leading to necrosis and formation of a cavity. Squamous cell carcinoma fits this pattern best: it originates in the bronchial epithelium, tends to be a central, hilar mass, and cavitation is a classic feature. Mediastinal widening can accompany a central tumor as it grows toward and compresses mediastinal structures.

Adenocarcinoma is more often peripheral and less likely to cavitate; mesothelioma involves the pleura with diffuse thickening or effusion rather than a central cavitating hilar mass; large cell carcinoma is frequently peripheral and cavitation is not as characteristic. Thus, the combination of a central/hilar mass with cavitation in a smoker most strongly points to squamous cell carcinoma.