A leg rash may transform into certain types of cancer, primarily skin cancer, and may indicate presence of other cancers, such as ovarian cancer, or signal other underlying illnesses, according to the American Academy of Dermatology. Some cancers, such as squamous cell skin cancer, present as rashes, and may have accompanying patches, itchy skin and bleeding. The type of rash, including color of skin and size, may determine its seriousness as can presence or absence of other symptoms relating to certain medical conditions.
According to the American Academy of Dermatology, skin abnormalities, including rashes, may serve as important indicators of physical illness. Sometimes, skin changes appear as early indicators of diseases, while in other cases, skin abnormalities appear after diseases take hold.
Rashes suddenly appearing on the legs or even feet might indicate an underlying infection or hepatitis C. Dermatologists suspect infections or hepatitis when rashes do not respond to treatment, usually involving creams and gels, and patients report other symptoms indicating infection, such as joint pain, muscle aches and fever.
Sometimes, skin rashes appear as early indicators of skin cancer. Bowen disease, an early form of squamous skin cancer, presents as a cluster of red or scaly skin patches. According to WebMD, patients might mistake these signs for common skin problems such as benign rashes, eczema and psoriasis. Regardless of rash size, experts recommend seeing a dermatologist for accurate diagnosis and treatment.