The main difference between a benign and a malignant or a cancerous tumor is its ability to spread. A cancer can invade tissues locally and spread to multiple organs in the body. This process of cancer spreading is called as metastasis. When such spread occurs it is usually called stage IV or metastatic disease and is the final stage of cancer. Patients may present with earlier stages of cancer and disease may progress by spreading to other sites or patients may have metastatic disease at presentation.
The mechanism of cancer spread can be by first invasion of nearby tissue, second by growing to channels of lymph and blood, third by movement through these channels into distant sites, fourth by outgrowth from these tumor cells into tissue and organs and fifth by forming a tumor mass at far away organs.
The most common sites of such spread are lung, liver and bones. The other common sites are brain,adrenal glands, skin and vagina. The site of spread depends on the nature of the tumor and location of the primary tumor. Depending on site of spread patient can have clinical symptoms which can be
- Bones -pains and fractures
- Lungs – Cough, breathlessness if lungs are involved
- Jaundice, pain abdomen if liver spread
- Loss of consciousness, altered sensorium and seizures
Most often such patients with advanced cancer are suitable for palliative treatment. The intent of it is to improve the quality of life by slowing the growth of cancer.