What do you think makes skin so susceptible to uncontrolled cellular growth?

Skin is most vulnerable to uncontrolled cellular growth as it gets exposed to the external environment and the possible carcinogens, the other factor is the rapid rate of mitosis, which would permit cancer or uncontrolled growth of cells to take place briskly.  

In the United States, skin cancer is the most usual form of cancer witnessed. Some of the individuals are at greater threat of skin cancer in comparison to others. The most general source of skin cancer is getting overexposed to UV light, either due to simulated sources like tanning beds or from the Sun. The two most general kinds of skin cancer are the squamous cell and the basal cell carcinomas.  

cells use diffusion to get substances in and out of themselves. that diffusion will occur across the cell membrane or the outer covering of the cell. because we are talking about the surface of the cell, surface area and volume are  important factors here. as a cell increases in size, its surface area and volume increase as well.  we call that the surface area to volume ratio (sa: vol).  but the catch is that  volume increases at a greater rate than surface  area. in other words, as a cell gets bigger, the sa: vol gets smaller. so a really small cell like bacteria is mostly cell membrane (surface) with very little contents (volume). a really big cell like an egg, is mostly insides with a super thin membrane. so what ends up happening is that the cell cannot efficiently diffuse all of the stuff it needs in/out to survive. therefore cell size is limited to about 100mm. so how do we make organisms bigger than 100mm? cells divide! by dividing and becoming multicellular, organisms are able to grow!   check out the diagrams i attached to see the effect of sa: vol. i hope this ! good luck!