Cancer metastasis occurs when malignant cells break away from a primary tumor and travel to distant parts of the body to form new growths. When this spread specifically targets the body’s major soft internal organs, it is defined as visceral metastasis. The term “viscera” encompasses organs within the body cavities, such as the lungs, liver, and brain. The presence of tumors in these sites signifies an advanced stage of the disease.
Understanding the Spread to Internal Organs
Visceral metastases are secondary tumors that form in the viscera, distinct from the primary tumor where the cancer originated. These secondary tumors are composed of the same type of cancer cells as the original tumor. For example, breast cancer that spreads to the liver is still treated as metastatic breast cancer, not liver cancer.
Cancer cells primarily travel from the primary site to the viscera via two major pathways: the bloodstream (hematogenous spread) and the lymphatic system (lymphatic spread). Hematogenous spread occurs when cancer cells penetrate blood vessel walls and circulate until they lodge in the capillaries of a distant organ. Lymphatic spread involves cancer cells entering lymphatic vessels and traveling through lymph nodes before potentially reaching the general circulation and distant organs.
Certain internal organs become common targets due to their physiological function, aligning with the “seed and soil” hypothesis of metastasis. Organs with high blood flow, such as the lungs and liver, act as filters that trap circulating tumor cells, making them frequent sites for secondary tumors. For instance, blood from the digestive tract passes through the liver, making it a common site for metastases from colon or pancreatic cancers. The organ’s environment (“soil”) must be hospitable for the cancer cells (“seed”) to successfully grow into a new tumor.
Common Sites and Resulting Clinical Signs
The organs most frequently affected by visceral metastasis include the lungs, liver, and brain. Lung metastases may manifest as a persistent cough, shortness of breath, or chest pain. These symptoms occur as the tumors grow and interfere with normal lung tissue and breathing mechanics.
Liver metastases can cause jaundice (yellowing of the skin and eyes) or pain and swelling in the abdominal area. These issues arise when growing tumors impair the liver’s ability to filter waste and process bile.
When cancer spreads to the brain, the symptoms are often neurological, including severe, persistent headaches, seizures, or changes in vision, speech, or balance. Because of the confined space inside the skull, even small tumors can increase pressure, leading to neurological deficits. Adrenal gland metastases are less frequent but may cause pain in the flank or abdomen, though they are often silent until they become large.
Confirming the Diagnosis Through Imaging and Biopsy
Detection of visceral metastases begins with clinical evaluation and advanced imaging techniques. Computed Tomography (CT) scans locate tumors in the chest, abdomen, and pelvis, determining their size and number. Magnetic Resonance Imaging (MRI) offers superior detail for soft tissues, making it valuable for detecting metastases in the brain or liver.
Positron Emission Tomography (PET) scans, often combined with CT (PET-CT), use a radioactive tracer to highlight areas of increased metabolic activity characteristic of rapidly growing cancer cells. These imaging modalities help physicians assess the full extent of the disease. However, imaging alone is usually not sufficient for a definitive diagnosis.
To confirm a newly discovered mass is metastatic, a biopsy is often required. A pathologist analyzes the tissue sample to verify the presence of cancer cells and confirm they match the primary tumor type. Histological analysis provides the specific biological information needed to select the most appropriate treatment, such as identifying molecular markers or genetic mutations.
Overview of Treatment Modalities
Treating visceral metastases requires a comprehensive approach aimed at controlling the disease and managing symptoms, as a cure is frequently not achievable. Treatment selection is highly individualized, depending on the type of primary cancer, the location and number of metastases, and the patient’s overall health.
Systemic therapies are body-wide treatments designed to kill cancer cells throughout the entire body. This includes chemotherapy, which uses powerful drugs to destroy fast-growing cells, and targeted therapy, which utilizes drugs that block specific molecules needed for tumor growth. Immunotherapy is a newer systemic approach that activates the patient’s own immune system to recognize and attack the cancer cells.
Localized treatments focus directly on metastatic tumors in specific organs to shrink them or alleviate symptoms. Radiation therapy uses high-energy beams to destroy cancer cells in a targeted area, often used for painful bone or brain metastases. In select cases, procedures like surgical removal of a single metastasis (oligometastasis) or ablation techniques, such as radiofrequency ablation, may be used to destroy tumors in the liver or lung while sparing healthy tissue.