system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why are some organs more likely to get cancer than others?
gpt
Cancer is a condition where cell DNA gets damaged, not enough to kill the cell, but enough to cause it to stop doing its job (as a neuron, liver cell, muscle cell, etc.) and start multiplying out of control.  So the issue is that the cell multiplies and multiplies, and eventually a good portion of your internal organ is composed of these cells that don't do their job, so the organ fails.

In any case, to answer your question, part of it is because some organs are more exposed to things that damage DNA.  Skin, for example, exposed to UV radiation, very high chance to get melanoma.  If your diet is composed of animals or plants that have grown in a polluted area, toxins may accumulate in your bones over time, and kill the bone marrow in your thigh bones, causing leukemia (the bone marrow no longer produces red blood cells).  Exposure to radiaton (x-rays, gamma rays) can cause DNA damage to the organ that was exposed.  Your digestive system and especially liver have to process every nutrient and chemical that enters your body, so DNA-damaging toxic chemicals are an issue.  Your lungs inhale air and smoke and dust, so again, smoking cigarettes for example can cause lung cancer.

And otherwise, as the others have said, the cells in some of your organs are specialized, and might have very short life spans and thus multiply a lot (to offset this).  Skin, blood cells, etc., the life span of these cells is measured in days, whereas neurons, muscle cells, etc., have a life span measured in years.  So if the cells multiply often, the cancer zone will grow and spread.