Rare, deadly, and often missed, some skin cancers develop in areas that rarely see the sun. Scientists are still learning about them, but here's what we know.

WebMD's COPD Health Center provides in-depth information on chronic obstructive pulmonary disease including symptoms, causes, treatment options, diagnosis, and tests.

High blood pressure affects I in 4 American adults. Find in-depth high blood pressure and hypertension information including its causes, symptoms, and treatments.