Squamous cell carcinoma marker is-
**Core Concept**
Squamous cell carcinoma (SCC) is a type of skin cancer characterized by the uncontrolled growth of squamous cells, which are a type of epithelial cell. The identification of specific markers is crucial for diagnosing and distinguishing SCC from other types of skin cancers.
**Why the Correct Answer is Right**
The correct marker for squamous cell carcinoma is cytokeratin 5/6 (CK5/6). This is because SCC cells often express high levels of CK5/6, which is a specific type of intermediate filament protein. CK5/6 is typically associated with the differentiation of squamous epithelial cells, and its expression is often used as a diagnostic marker for SCC in histopathological examinations.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because cytokeratin 7 (CK7) is more commonly associated with adenocarcinomas, such as breast and lung cancer.
* **Option B:** This option is incorrect because cytokeratin 20 (CK20) is more commonly associated with neuroendocrine tumors, such as small cell carcinoma of the lung.
* **Option C:** This option is incorrect because epithelial membrane antigen (EMA) is a more general marker for epithelial cells, and its expression is not specific to SCC.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the expression of specific cytokeratins can help differentiate between various types of skin cancers. CK5/6 is a reliable marker for SCC, but other cytokeratins, such as CK7 and CK20, can help identify other types of skin cancers.
**Correct Answer:** C. Cytokeratin 5/6 (CK5/6)