About 75 percent of<unk>  is caused by the illness itself; most of the remainder is caused by diagnostic procedures and treatment. Tumor-related Tumors cause pain by crushing or infiltrating tissue, triggering infection or inflammation, or releasing chemicals that make normally non-painful stimuli painful. Invasion of bone by cancer is the most common source of<unk> . It is usually felt as tenderness, with constant background pain and instances of spontaneous or movement-related exacerbation, and is frequently described as severe. Rib fractures are common in breast, prostate and other cancers with rib metastases. The vascular (blood) system can be affected by solid tumors. Between 15 and 25 percent of deep vein thrombosis is caused by cancer (often by a tumor compressing a vein), and it may be the first hint that cancer is present. It causes swelling and pain in the legs, especially the calf, and (rarely) in the arms. The superior vena cava (a large vein carrying circulating, de-oxygenated blood into the heart) may be compressed by a tumor, causing superior vena cava syndrome, which can cause chest wall pain among other symptoms. When tumors compress, invade or inflame parts of the nervous system (such as the brain, spinal cord, nerves, ganglia or plexa), they can cause pain and other symptoms. Though brain tissue contains no pain sensors, brain tumors can cause pain by pressing on blood vessels or the membrane that encapsulates the brain (the meninges), or indirectly by causing a build-up of fluid (edema) that may compress pain-sensitive tissue. Pain from cancer of the organs, such as the stomach or liver (visceral pain), is diffuse and difficult to locate, and is often referred to more distant, usually superficial, sites. Invasion of soft tissue by a tumor can cause pain by inflammatory or mechanical stimulation of pain sensors, or destruction of mobile structures such as ligaments, tendons and skeletal muscles. Pain produced by cancer within the pelvis varies depending on the affected tissue. It may appear at the site of the cancer but it frequently radiates diffusely to the upper thigh, and may refer to the lower back, the external genitalia or perineum. Diagnostic procedures Some diagnostic procedures, such as lumbar puncture (see post-dural-puncture headache), venipuncture, paracentesis, and thoracentesis can be painful. Treatment-related Chemotherapy drugs Potentially painful cancer treatments include: *immunotherapy which may produce joint or muscle pain; *radiotherapy, which can cause skin reactions, enteritis, fibrosis, myelopathy, bone necrosis, neuropathy or plexopathy; *chemotherapy, often associated with chemotherapy induced peripheral neuropathy, mucositis, joint pain, muscle pain, and abdominal pain due to diarrhea or constipation; *hormone therapy, which sometimes causes pain flares; *targeted therapies, such as trastuzumab and rituximab, which can cause muscle, joint or chest pain; *angiogenesis inhibitors like bevacizumab, known to sometimes cause bone pain; *surgery, which may produce post-operative pain, post-amputation pain or pelvic floor myalgia. Infection The chemical changes associated with infection of a tumor or its surrounding tissue can cause rapidly escalating pain, but infection is sometimes overlooked as a possible cause. One study found that infection was the cause of pain in four percent of nearly 300 people with cancer who were referred for pain relief. Another report described seven people with cancer, whose previously well-controlled pain escalated significantly over several days. Antibiotic treatment produced pain relief in all of them within three days.
Cancer pain
Chronic pain
Cancer signs and symptoms
Cancer syndrome
Chronic wound pain
Psychogenic pain
Visceral pain
Stroke recovery