Squamous cell carcinoma develops in which levels of the epidermis?

Squamous cell carcinoma (SCC) primarily originates from the keratinocytes in the upper layers of the epidermis. Specifically, it develops in the stratum spinosum and stratum granulosum, which are considered the higher levels of the epidermis. This is important because these layers are responsible for the more advanced differentiation of skin cells, ultimately leading to the formation of the type of cells that can become cancerous when subjected to various risk factors, such as UV radiation, chemicals, or chronic irritation.

Understanding this context helps clarify that while the lower layers of the epidermis are where initial skin cell generation occurs, the transformation to SCC occurs when there are genetic mutations in the keratinocytes that have moved up into the higher layers. This cancer can become invasive and spread, making early detection and treatment critical, particularly in the higher layers where it is most likely to develop.