Colon cancer symptoms on skin: What you need to know

Colon cancer, also called colorectal cancer, mainly affects the large intestine and rectum. It is among the most common cancers in the UK and globally. While digestive symptoms like changes in bowel habits and abdominal pain are well known, colon cancer can also cause symptoms on the skin, though these are rare. Skin signs such as nodules, rashes, ulcers, or changes in pigmentation may indicate the cancer has spread or is progressing. Recognising these skin symptoms early can be crucial for timely diagnosis and treatment, improving outcomes for those affected by this disease.



How colon cancer can affect the skin
Colon cancer originates in the colon lining but can spread beyond the primary site. In advanced stages, cancer cells may metastasise (spread) to other parts of the body, including the skin. Skin symptoms related to colon cancer may be due to:

• Direct metastasis to the skin
• Paraneoplastic syndromes (indirect effects of cancer through immune or hormonal responses)
• Side effects of cancer treatments

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Common skin symptoms linked to colon cancer
According to a study published in the National Center for Biotechnology Information (NCBI), skin manifestations in colon cancer patients, such as nodules and rashes, often indicate metastatic spread and can serve as important clinical signs for early diagnosis and treatment planning.

Recognising these symptoms promptly may improve patient outcomes by facilitating timely intervention.


1. Skin nodules or lesions

One of the most recognised skin symptoms of colon cancer metastasis is the appearance of firm, painless nodules or lumps on the skin. These lesions can vary in colour, often reddish, purple, or skin-toned, and may appear anywhere but are frequently found on the abdomen, chest, or around surgical scars.


2. Skin rash or erythema

In some cases, colon cancer may trigger a rash or persistent redness known as erythema. This can be due to paraneoplastic syndromes, where the immune system reacts abnormally to the presence of cancer.


3. Skin ulcers and infections

Cancerous lesions on the skin can break down, forming ulcers or open sores that are slow to heal. These can become sites of secondary infection, causing pain and discomfort.


4. Hyperpigmentation and other changes

Rarely, patients may experience changes in skin colour or texture, including darkening (hyperpigmentation) or thickening of the skin.



Why do skin symptoms occur

• Metastasis: Colon cancer cells travel through the bloodstream or lymphatic system and settle in the skin, forming secondary tumours.
• Immune response: The body’s reaction to the cancer can produce paraneoplastic skin conditions.
• Treatment effects: Chemotherapy and radiotherapy can cause skin dryness, rashes, and sensitivity.

According to the National Center for Biotechnology Information, cutaneous metastases from colon cancer occur in approximately 3-6% of patients, indicating a poor prognosis but providing important clinical clues.



When to see a doctor
If you notice unusual skin changes such as persistent lumps, sores that don’t heal, or unexplained rashes, especially if you have a history of colon cancer or related symptoms (e.g., changes in bowel habits, abdominal pain, unexplained weight loss), it is essential to consult a healthcare professional promptly.

Early detection can significantly improve treatment outcomes.



Disclaimer: This article is for informational purposes only and does not replace professional medical advice, diagnosis, or treatment. Always consult your healthcare provider for personalised guidance regarding any medical condition.




Also read | Colon cancer risk factors: What increases your chances?