Squamous cell carcinomas occur in which layer of the epidermis?

Squamous cell carcinomas occur in which layer of the epidermis?

• A. Stratum spinosum
• B. Stratum basale
• C. Stratum granulosum
• D. Stratum lucidum

Answer: (A)

Squamous cell carcinoma arises from squamous keratinocytes in the epidermis, most classically the cells in the stratum spinosum. This layer sits above the basal layer and contains keratinocytes that have started to differentiate into squamous cells and are connected by desmosomes, giving the characteristic spiny appearance. Basal cell carcinoma comes from the basal layer (stratum basale), while the stratum lucidum is present only in thick skin and is not the usual origin for this cancer; the granulosum is a differentiation stage, not the typical site of origin. Therefore, the best answer is the stratum spinosum.

Squamous cell carcinoma arises from squamous keratinocytes in the epidermis, most classically the cells in the stratum spinosum. This layer sits above the basal layer and contains keratinocytes that have started to differentiate into squamous cells and are connected by desmosomes, giving the characteristic spiny appearance. Basal cell carcinoma comes from the basal layer (stratum basale), while the stratum lucidum is present only in thick skin and is not the usual origin for this cancer; the granulosum is a differentiation stage, not the typical site of origin. Therefore, the best answer is the stratum spinosum.