Squamous cell carcinoma spreads by
**Core Concept**
Squamous cell carcinoma (SCC) is a type of skin cancer that originates from the squamous epithelial cells. The spread of SCC involves the process of metastasis, where cancer cells invade surrounding tissues and eventually reach distant sites through the bloodstream or lymphatic system.
**Why the Correct Answer is Right**
SCC primarily spreads through the lymphatic system, which is a network of vessels responsible for draining excess fluids, proteins, and cells from the body. When SCC cells invade the lymphatic vessels, they can be carried to regional lymph nodes, where they may establish secondary tumors. This process is facilitated by the expression of lymphatic endothelial growth factors and the interaction between SCC cells and lymphatic endothelial cells.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while SCC can also spread through the bloodstream, lymphatic spread is the primary route for this type of cancer.
**Option B:** This option is incorrect because direct extension through adjacent tissues is more characteristic of other types of cancers, such as basal cell carcinoma or melanoma.
**Option C:** This option is incorrect because while SCC can invade surrounding tissues, this option does not accurately describe the primary mechanism of spread.
**Clinical Pearl / High-Yield Fact**
It's essential to note that the primary site of metastasis for SCC often correlates with the location of the primary tumor. For example, SCC of the head and neck region often metastasizes to the cervical lymph nodes, while SCC of the skin often metastasizes to the regional lymph nodes closest to the primary tumor site.
**Correct Answer:** C.