This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
Squamous cell carcinoma can arise from-a) Long standing venous ulcersb) Chronic lupus vulgarisc) Rodent ulcerd) All of the above 
Select and explain. 
A. ac, B. a, C. ab, D. bc
C: ab
Answer: C: ab 
Explanation: • It is a carcinoma of the cells of epidermis that usually migrate outwards to the surface.
• Originate from prickle cell layer; Seen in > 40 years of age
• MC skin cancer in darkly pigmented races
• 2nd MC skin cancer in light skinned races
• MC causative factor: Sunlight
• MC site: Ears, cheeks, lower lip and back of hands