A 60 year old male had a chronic history of exposure of asbestosis. He now presents with a mass in the apex of right lung. Which of the following would be seen on electron microscopy of a biopsy from the lesion?
**Core Concept**
The question is testing the understanding of the pathophysiology of malignant mesothelioma, a type of cancer associated with asbestos exposure. Malignant mesothelioma is a rare but aggressive tumor that arises from the mesothelial cells lining the pleura, peritoneum, or pericardium.
**Why the Correct Answer is Right**
In malignant mesothelioma, the mesothelial cells undergo malignant transformation, leading to the formation of abnormal cell structures. Electron microscopy is a valuable tool for diagnosing mesothelioma, as it allows for the visualization of characteristic ultrastructural features of the tumor cells. Specifically, the presence of long, thin, and branching microvilli, also known as "carina-like" microvilli, is a hallmark of malignant mesothelioma. This feature is a result of the abnormal expression of microvilli-associated proteins and is a key diagnostic criterion.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option does not describe a characteristic feature of malignant mesothelioma on electron microscopy. While some tumors may exhibit long microvilli, this is not specific to mesothelioma.
* **Option B:** This option is incorrect as it describes a feature of adenocarcinoma, a different type of lung cancer. Adenocarcinoma cells often exhibit short, stubby microvilli, but not the characteristic long, thin microvilli seen in mesothelioma.
* **Option C:** This option does not accurately describe a feature of malignant mesothelioma on electron microscopy. While some tumors may exhibit short microvilli, this is not a characteristic feature of mesothelioma.
**Clinical Pearl / High-Yield Fact**
Malignant mesothelioma is a highly aggressive tumor with a poor prognosis. Early diagnosis is crucial, and electron microscopy can play a critical role in confirming the diagnosis. It is essential for clinicians to be aware of the characteristic ultrastructural features of mesothelioma to make an accurate diagnosis.
**Correct Answer:** C.