How Cancer Affects the Foot

Cancer, a disease characterized by uncontrolled cell growth, can manifest in virtually any part of the body, including the foot—a site often overlooked due to its rarity. While cancers of the foot account for less than 1% of all malignancies, their impact can be profound, disrupting mobility, causing chronic pain, and potentially leading to amputation if untreated. The foot's unique anatomy, bearing weight and enduring constant friction, makes it vulnerable to both primary cancers originating there and secondary ones spreading from elsewhere. Primary forms include skin cancers like melanoma and squamous cell carcinoma, as well as bone and soft tissue sarcomas. Metastatic cancers, though even rarer, add another layer of complexity. Understanding these effects is crucial for early intervention, as foot cancers are frequently misdiagnosed as benign conditions like warts or sprains. This essay explores the symptoms, physiological impacts, diagnosis, and treatments of foot cancers, highlighting why vigilance is essential for preserving function and quality of life.

Skin cancers represent the most common malignancies affecting the foot, often arising from chronic irritation rather than sun exposure, given the area's limited UV contact. Basal cell carcinoma, the least aggressive type, appears as pearly white bumps or crusty patches that may ooze, mimicking benign ulcers or tumors. It causes localized tissue destruction but rarely metastasizes. Squamous cell carcinoma, more prevalent on the feet, begins as scaly plaques or inflamed bumps with a history of cracking, bleeding, or ulceration, often resembling plantar warts, fungal infections, or eczema. If advanced, it invades deeper tissues, leading to bone erosion and gait alterations. Malignant melanoma, the deadliest form, is particularly insidious in the foot, where it manifests as acral lentiginous melanoma (ALM)—a subtype comprising 2-3% of all melanomas and disproportionately affecting non-white individuals. Symptoms follow the ABCDE rule: asymmetry, irregular borders, varied colors (black, brown, red, or even pink in amelanotic cases), diameter over 6 mm, and evolving changes. On the soles, between toes, or under toenails, it may present as dark streaks, bruises, or itchy lesions that bleed or scale. These growths start in the epidermis but thicken, infiltrating subcutaneous layers and disrupting the foot's cushioning fat pads, causing pain during weight-bearing and increasing infection risk from cracks. Untreated, melanoma spreads to lymph nodes or distant organs, severely compromising foot function and overall survival. Diagnosis relies on podiatric examination and biopsy, where a sample is analyzed for malignancy. Treatments vary by stage: early excision removes the lesion with margins, while advanced cases demand Mohs surgery, chemotherapy, immunotherapy to boost immune attack, or radiation. Prevention emphasizes sunscreen on exposed ankles and prompt evaluation of persistent sores.

Beyond the skin, primary bone and soft tissue cancers in the foot, such as osteosarcoma and Ewing's sarcoma, strike younger populations and exert devastating mechanical effects. Osteosarcoma, the most common bone cancer, originates in osteoblasts and often targets long bones like the metatarsals or phalanges. Initial symptoms include persistent, throbbing bone pain worsening at night, swelling, tenderness, and a palpable lump—frequently mistaken for injury-related issues. As the tumor grows, it weakens bone integrity, leading to pathological fractures that hobble patients and alter biomechanics, straining the ankle and knee. Soft tissue sarcomas, like synovial sarcoma in tendons or ligaments, present similarly with painless masses that evolve into firm, tender nodules restricting joint motion. These cancers erode surrounding structures, compressing nerves and vessels, which can cause numbness, vascular insufficiency, or chronic wounds. The foot's role in propulsion amplifies these effects, resulting in limping, instability, and secondary issues like calluses or ulcers from uneven pressure distribution. Diagnosis involves imaging—X-rays reveal lytic lesions, while MRI assesses soft tissue involvement—followed by biopsy for confirmation. Staging determines prognosis; localized tumors have a 60-70% five-year survival rate. Treatment is multimodal: neoadjuvant chemotherapy shrinks tumors pre-surgery, followed by wide resection or limb-sparing procedures to preserve function, though partial foot amputation may be necessary for aggressive cases. Radiation targets residuals, but side effects like fibrosis further stiffen tissues. Early detection via routine checks is vital, as delays exacerbate bone destruction and metastasis risk.

Metastatic cancers to the foot, occurring in just 0.007-0.3% of cases, signal advanced disease and pose unique diagnostic hurdles. Primarily from lung (28%), endometrial (17%), or breast (11%) primaries, they lodge in weight-bearing bones like the calcaneus or talus, presenting with non-specific signs: soft tissue swelling, erythema, intermittent pain, ulcers, or functional decline. These mimic podiatric ailments—heel spurs, fasciitis, or gout—delaying recognition by months. The impact is palliative-focused; tumors fracture bones, inflame synovium, and impair proprioception, confining patients to wheelchairs and diminishing independence. In 37% of instances, foot lesions herald an occult primary, complicating care. Diagnosis employs X-rays (80% initial use), CT/MRI for extent, bone scans for multifocality, and biopsy (91% of cases). Treatment emphasizes symptom control: radiotherapy alleviates pain in 61% of patients, surgery (curettage or amputation) restores stability in select cases, and systemic therapies like chemotherapy target the source. Multidisciplinary teams tailor approaches, prioritizing quality over cure given dismal prognoses.

Cancer's toll extends systemically; paraneoplastic syndromes from distant tumors may induce peripheral neuropathy, manifesting as foot tingling or weakness, while treatments like chemotherapy cause plantar desquamation or lymphedema, exacerbating swelling and infection vulnerability.

Cancer profoundly disrupts the foot's biomechanics, from localized erosion to global mobility loss, underscoring the need for awareness. Routine self-exams and professional vigilance can transform outcomes, turning potential tragedies into manageable conditions. By demystifying these effects, we empower proactive health stewardship.

Craig Payne is a University lecturer, runner, cynic, researcher, skeptic, forum admin, woo basher, clinician, rabble-rouser, blogger and a dad.