Metastasis

Metastasis, or metastatic cancer, occurs when tumor cells spread through the bloodstream or lymphatic vessels to an organ different from the one where they originated, forming secondary tumors.

Metastatic cancer can be classified into three types depending on the extent of dissemination:

• Local metastasis: cancer cells have spread to nearby tissues or regional lymph nodes.
• Regional metastasis: the tumor has reached adjacent organs, meaning the cancer remains within the same anatomical area.
• Distant metastasis: tumor cells have spread to remote organs.

Considering tumor size, metastasis can also be described as:

• Micrometastasis: small clusters of cancer cells forming tumors between 0.2 and 2 millimeters, often undetectable by imaging techniques.
• Macrometastasis: the general term "metastasis" usually refers to this type, involving tumor cell dissemination forming lesions larger than 2 millimeters.

Contrary to common belief, metastatic tumors retain the histological and molecular characteristics of the primary tumor, even when they develop in a different organ. For instance, if lung cancer spreads to the bones, it is classified as lung cancer with bone metastasis, not bone cancer.

Metastasis generally carries a worse prognosis than the primary tumor. Nevertheless, advances in oncologic treatments over recent years have enabled the cure of certain metastatic cancers or a significant slowing of disease progression for several years.

Symptoms

Metastatic cancer may be asymptomatic. When symptoms occur, they vary widely depending on the location and nature of the metastasis. The most common and generalized manifestations include:

• Persistent pain, either localized or generalized.
• Unintentional weight loss.
• Fever of unknown origin.
• Fatigue.

Among the most frequent types of metastasis, characteristic symptoms include:

• Hepatic metastasis: occurs when cancer cells reach the liver:
  • Loss of appetite.
  • Jaundice: yellowish discoloration of the skin, mucous membranes, or sclera.
  • Nausea.
  • Abdominal pain.
  • Confusion.
• Pulmonary metastasis: the cancer spreads to the lungs:
  • Dyspnea: difficulty breathing.
  • Shortness of breath.
  • Dry, persistent cough.
  • Hemoptysis: coughing up blood.
  • Chest pain.
• Bone metastasis: tumor cells spread and proliferate within the bone tissue:
  • Bone pain.
  • Pathological fractures.
  • Weakness in the extremities.
  • Hypercalcemia: elevated calcium levels in the blood.
• Brain metastasis: the cancer disseminates to the brain:
  • Headache.
  • Loss of balance.
  • Visual disturbances.
  • Seizures.
  • Nausea and vomiting.
  • Memory loss.
  • Numbness or paralysis of one side of the body.

Causes

The mechanisms by which cancer spreads to other parts of the body remain unclear despite scientific advances. Some studies suggest that the metastatic potential of cancer cells increases due to genetic mutations within the tumor itself or abnormal interactions between tumor cells and surrounding tissues.

Risk Factors

The main risk factor for developing metastasis is having cancer. Each type of tumor has a predilection for spreading to specific organs:

• Hepatic metastasis: lymphoma, leukemia, lung, breast, colon, pancreatic, or gastric cancer.
• Pulmonary metastasis: nearly any type of cancer can spread to the lungs.
• Bone metastasis: lymphoma, multiple myeloma, breast, renal, lung, thyroid, or prostate cancer.
• Brain metastasis: melanoma, breast, lung, colon, or kidney cancer.

Complications

Uncontrolled metastasis affects vital organs, leading to their progressive failure. This terminal phase, which varies in duration depending on each case, ultimately results in death.

Prevention

Metastasis cannot be prevented. However, certain lifestyle habits may help reduce the likelihood of cancer cell proliferation:

• Balanced, healthy diet, rich in fruits and vegetables; limiting red meat and avoiding processed foods.
• Regular moderate exercise to improve mood and reduce stress-related symptoms.
• Avoid smoking.
• Attend regular follow-up appointments as recommended by the oncologist.

Which Specialist Treats Metastasis?

Oncologists are the specialists responsible for diagnosing and assessing the severity of metastasis. Treatment involves a multidisciplinary medical team including specialists in the affected organs. In advanced-stage metastasis, patients are referred to palliative care services.