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A woman talking to her doctor about a rash

A skin rash can develop for many reasons, most of which are unrelated to cancer. Even so, a rash could be a sign of an underlying medical condition that requires treatment, such as an allergy or infection. Therefore, any unusual skin changes should be promptly discussed with a physician.

Rashes & skin cancer

Not all types of skin cancer cause a rash. For example, melanoma - which develops in the melanocyte cells that provide pigment to the skin - more often resembles a misshapen mole than a rash.

On the other hand, the first sign of basal cell carcinoma is usually a scaly, pink skin patch or a pearly bump that grows larger and becomes shinier over time. As the cancer progresses, an indentation may form in the center of the lesion, where it may begin to ooze or bleed.

Initially, a rash caused by basal cell carcinoma may resemble dermatitis, psoriasis or eczema. However, unlike a noncancerous skin rash, a cancerous skin rash will usually not resolve on its own.

Rashes & other types of cancer

Less commonly, a rash may be caused by a type of cancer other than skin cancer, such as:

  • Leukemia – A blood cancer that develops in the bone marrow, leukemia is caused by the rapid production of abnormal white blood cells, which impair the body’s ability to produce red blood cells and platelets. A low platelet count can lead to easy bruising and bleeding, and broken capillaries under the skin can cause tiny red spots to form on the skin’s surface (petechiae) that resemble a rash.
  • Mycosis fungoides – A type of cutaneous T cell lymphoma, mycosis fungoides occurs when certain white blood cells (lymphocytes) undergo cancerous changes that cause them to attack the skin. The early signs include itchy, rash-like skin patches, which may form sores and tumors as the cancer progresses.
  • Sézary syndrome – A leukemic variant of mycosis fungoides, Sézary syndrome causes an extensive, itchy red rash over at least 80% of the body.
  • Kaposi sarcoma – A type of cancer that develops in the cells that line lymphatic and blood vessels, Kaposi sarcoma can cause deep red, purple, or brown lesions to form on the skin’s surface.

Seek a diagnosis

If you have a persistent skin rash of any kind, you should see a physician - even if you feel confident that you know the cause. This is the best way to ensure that you will receive appropriate treatment, if necessary, and also avoid complications related to a misdiagnosis.

You can discuss your skin cancer symptoms with a specialist in the Cutaneous Oncology Program at Moffitt Cancer Center. To request an appointment, call 1-888-663-3488 or complete our new patient registration form online.