While the feet are often overlooked in discussions about oncology, they are frequently the site of significant complications—ranging from the cancer itself to the side effects of life-saving treatments.1 Because the feet are essential for mobility, any oncological impact on them directly affects a patient’s independence and quality of life.2
Cancer affects the feet through three primary pathways: primary tumors originating in the foot, metastatic spread from distant organs, and systemic side effects of cancer therapies.
1. Primary Cancers of the Foot
Primary cancers—those that start in the foot—can involve the skin, soft tissues, or bones.3 These are often difficult to diagnose because they mimic common, benign foot conditions.4
Skin Cancers
The foot is a frequent site for various skin malignancies, and because it is often covered by socks and shoes, these lesions can go unnoticed for long periods.5
- Malignant Melanoma: This is the most dangerous foot cancer.6 It often appears on the soles or under the toenails (subungual melanoma).7 It may look like a simple bruise, a dark streak under the nail, or a changing mole.8
- Squamous Cell Carcinoma: This is the most common form of foot cancer.9 It often presents as a scaly, red patch or a non-healing ulcer.10 It is frequently mistaken for a fungal infection or a stubborn plantar wart.11
- Basal Cell Carcinoma: Though less common on the feet than on sun-exposed areas like the face, it can still occur, appearing as a pearly bump or a sore that bleeds and scabs but never fully heals.12
Bone and Soft Tissue Sarcomas
The feet contain many small bones and a complex network of connective tissues.
- Osteosarcoma and Ewing’s Sarcoma: These rare bone cancers can occur in the feet, particularly in adolescents and young adults. They typically cause deep, aching pain and swelling that is often dismissed as a “growing pain” or a sports injury.
- Synovial Sarcoma: This is a slow-growing cancer of the soft tissues near the joints. It often presents as a painless lump, making it easy to ignore until it begins to interfere with shoe fit or joint movement.
2. Metastatic Cancer (Acrometastasis)
It is rare for cancer from other parts of the body to spread to the feet, a phenomenon known as acrometastasis. However, when it does occur, it is usually a sign of advanced disease.
The most common primary cancers that metastasize to the feet are lung, colon, and kidney cancers. Because these tumors grow within the bone or soft tissue of the foot, they cause intense, “non-mechanical” pain—meaning the pain persists even when the person is resting. This can lead to “pathologic fractures,” where the bone becomes so weakened by the cancer that it breaks under the simple pressure of walking.
3. The Impact of Cancer Treatment
Often, the most profound impact on the feet comes not from the cancer itself, but from the treatments used to fight it.
Chemotherapy-Induced Peripheral Neuropathy (CIPN)
Many chemotherapy drugs (such as taxanes and platinum-based agents) are toxic to nerve fibers.13 This damage typically starts at the furthest points of the body—the toes.
- Symptoms: Patients experience tingling (“pins and needles”), burning, or total numbness.
- Consequences: Loss of sensation is dangerous; a patient might step on a sharp object or develop a blister without feeling it, leading to infections. Furthermore, the loss of “proprioception” (the brain’s ability to know where the feet are) significantly increases the risk of falls.14
Hand-Foot Syndrome (Palmar-Plantar Erythrodysesthesia)
Certain drugs, like capecitabine or 5-fluorouracil, leak out of the small capillaries in the palms and soles.15 This causes redness, swelling, and extreme tenderness. In severe cases, the skin may peel or blister, making the simple act of standing excruciatingly painful.
Lymphedema
When cancer affects the lymph nodes in the groin or pelvis—or when those nodes are removed surgically—the drainage of fluid from the legs is impaired.16 This leads to lymphedema, a chronic, heavy swelling of the legs and feet. This swelling can make the skin tight and “shiny,” increase the risk of skin infections (cellulitis), and make it impossible to wear standard footwear.
Summary Table: Common Foot Manifestations
| Cause | Typical Presentation | Often Mistaken For |
| Melanoma | Dark streak under nail or irregular sole lesion | Bruise or fungal nail |
| Squamous Cell | Non-healing ulcer or scaly patch | Plantar wart or eczema |
| Neuropathy | Burning, tingling, or numbness | Diabetes or “tired feet” |
| Sarcoma | Deep bone pain or firm lump | Sports injury or cyst |
| Metastasis | Severe pain and swelling | Gout or arthritis |
Cancer’s effect on the feet is multifaceted, impacting everything from the integrity of the skin to the stability of a person’s gait.17 Because many of these symptoms—such as a non-healing sore or a tingling sensation—seem minor, they are frequently misdiagnosed.
For cancer patients and survivors, “foot health” is not merely a matter of comfort; it is a vital component of their overall treatment and recovery. Early detection of foot lesions and proactive management of treatment side effects like neuropathy can prevent long-term disability and keep patients mobile during their journey.