Chest X-ray of an industrial worker exposed to asbestos over 20 years shows an ill-defined rounded opacity in the lower lobe with a ‘comet tail’ appearance on PA view. Which of the following is the most likely diagnosis-
**Core Concept**
Asbestos exposure is a known risk factor for the development of malignant pleural mesothelioma, a rare but aggressive tumor of the pleura. The "comet tail" appearance on chest X-ray is a characteristic radiographic feature of pleural plaques, which are benign but asbestos-induced lesions.
**Why the Correct Answer is Right**
The "comet tail" appearance is due to the presence of calcified pleural plaques, which are areas of fibrosis and calcification in the pleura. These plaques are thought to result from the chronic inflammatory response to asbestos fibers. In this case, the "comet tail" appearance is likely due to the presence of pleural plaques, which are benign but characteristic of asbestos exposure.
**Why Each Wrong Option is Incorrect**
* **Option A:** Malignant pleural mesothelioma would typically present with more extensive pleural thickening and nodularity, rather than a single rounded opacity with a "comet tail" appearance.
* **Option B:** Pulmonary asbestosis would typically present with bilateral interstitial lung disease, rather than a single rounded opacity in the lower lobe.
* **Option C:** Pleural effusion would typically present with fluid in the pleural space, rather than a solid rounded opacity with a "comet tail" appearance.
**Clinical Pearl / High-Yield Fact**
Asbestos exposure is a significant risk factor for the development of malignant pleural mesothelioma, and the presence of pleural plaques on chest X-ray is a characteristic feature of asbestos exposure. However, not all pleural plaques are due to asbestos exposure, and a thorough occupational history is necessary to determine the underlying cause.
**Correct Answer:** C.