A 56 year old chronic smoker, mass in bronchus resected. What is the possible marker?
**Core Concept**
The question is testing for a tumor marker associated with a type of cancer that commonly presents in the bronchus of a chronic smoker. This marker should be elevated in the patient's serum or tissue.
**Why the Correct Answer is Right**
The correct answer is related to a tumor marker for squamous cell carcinoma, which is a common type of lung cancer in smokers. Squamous cell carcinoma arises from the epithelial lining of the bronchus and is often associated with chronic smoking. The tumor marker in question is typically elevated in patients with this type of cancer due to its role in cell proliferation and tumor growth.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it is associated with a different type of cancer, such as colon cancer, and is not typically elevated in squamous cell carcinoma of the lung.
* **Option B:** This option is incorrect because it is a marker for a different type of cancer, such as breast cancer, and is not commonly associated with lung cancer.
* **Option C:** This option is incorrect because it is a marker for a different type of cancer, such as pancreatic cancer, and is not typically elevated in squamous cell carcinoma of the lung.
**Clinical Pearl / High-Yield Fact**
A key aspect of lung cancer diagnosis is the use of tumor markers to aid in diagnosis and monitoring. However, it is essential to note that tumor markers are not specific to a particular type of cancer and can be elevated in other conditions. A thorough clinical history, physical examination, and imaging studies are essential for accurate diagnosis.
**Correct Answer: D. CYTOKERATIN (CYFRA 21-1)**