This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Radiology
Atelectasis with reverse S sign is seen in 
Select and explain. 
A. Asthma, B. Tuberculosis, C. Sarcoidosis, D. Bronchogenic carcinoma
D: Bronchogenic carcinoma
Answer: D: Bronchogenic carcinoma 
Explanation: The Golden S-sign is seen on both PA chest radiographs and on CT scans. It is named because this sign resembles a reverse S shape, and is therefore sometimes referred to as the reverse S-sign of Golden. Although typically seen with right upper lobe collapse, the S-sign can also be seen with the collapse of other lobes. It is created by a central mass obstructing the upper lobe bronchus and should raise suspicion of a primary bronchogenic carcinoma. It can also be caused by other central masses, such as metastasis, primary mediastinal tumour, or enlarged lymph nodes(Grainger&;s diagnostic radiology, 6th ed, 328)