Cancer is characterized by the uncontrolled growth and division of abnormal cells. While many associate cancer with a palpable lump, these abnormal cells do not always form a solid mass. Certain types of cancer can exist and spread throughout the body without developing into a solid tumor. Understanding this distinction is important for diagnosis and management.
Understanding Tumors
A tumor is an abnormal mass of tissue from uncontrolled cell proliferation. Tumors can develop in almost any part of the body. Not all tumors are cancerous; they are classified as either benign or malignant. Benign tumors are non-cancerous, grow slowly, and typically do not invade surrounding tissues or spread. Malignant tumors are cancerous and can invade nearby tissues and spread to distant sites through the bloodstream or lymphatic system, a process known as metastasis.
Many common cancers, such as carcinomas and sarcomas, typically form solid tumors. These masses are often what people associate with cancer. However, their absence does not rule out cancer.
Cancers Without Solid Tumors
Some cancers primarily affect the blood, bone marrow, or lymphatic system, and do not form solid masses. These are often called “liquid cancers.”
Leukemia begins in blood-forming tissues, specifically the bone marrow. The body produces abnormal white blood cells that do not mature properly. These cancerous cells circulate in the bloodstream and bone marrow, crowding out healthy blood cells. This overgrowth impairs the bone marrow’s ability to produce normal red blood cells, white blood cells, and platelets.
Lymphoma originates in the lymphatic system, a network of vessels and nodes that are part of the body’s immune system. While lymphoma can cause enlarged lymph nodes, it can also involve organs like the spleen or bone marrow, spreading systemically. Cancerous lymphocytes accumulate in the lymph nodes or other lymphatic tissues.
Multiple myeloma is a cancer of plasma cells, specialized white blood cells found in the bone marrow. Abnormal plasma cells multiply uncontrollably in the bone marrow, producing dysfunctional proteins and damaging bone tissue. This leads to widespread bone lesions.
How Non-Solid Cancers Are Diagnosed
Diagnosing cancers that do not form solid tumors requires different approaches than those for solid masses. Medical professionals examine affected bodily fluids and tissues.
Blood tests are a fundamental diagnostic tool. A complete blood count (CBC) can detect abnormal numbers of red blood cells, white blood cells, or platelets, indicating leukemia or other blood cancers. Specialized blood tests can also identify abnormal proteins, such as the “M protein” in multiple myeloma, or markers suggesting a blood disorder.
Bone marrow biopsy and aspiration are procedures for diagnosing leukemias and multiple myeloma. A small sample of liquid bone marrow (aspiration) and a core of solid bone marrow tissue (biopsy) are collected, usually from the hip bone. These samples are examined under a microscope to identify cancerous cells and assess blood-forming tissue health.
For lymphoma, a lymph node biopsy is often necessary. This involves removing all or part of an enlarged lymph node for microscopic examination to confirm the type of lymphoma cells. Enlarged lymph nodes are a common manifestation of lymphoma. Imaging tests, such as PET scans or CT scans, can also identify enlarged lymph nodes or affected organs in non-solid cancers.
The Significance of This Distinction
Understanding that cancer can exist without forming a solid tumor is important for several reasons. The symptoms of non-solid cancers can be more general and less specific than those associated with a palpable lump. Individuals might experience fatigue, unexplained fever, night sweats, or weight loss, which can be attributed to many other conditions. This can sometimes lead to a longer diagnostic pathway compared to cancers with an obvious mass.
Treatment strategies also differ significantly. Solid tumors are often treated with localized therapies such as surgery or radiation therapy targeted at the tumor site. In contrast, non-solid cancers, which involve the blood or lymphatic system, are typically treated with systemic therapies that affect the entire body. These include chemotherapy, immunotherapy, or stem cell transplants, designed to eliminate cancerous cells circulating throughout the body or residing in the bone marrow. Monitoring and management often involve ongoing blood tests and bone marrow evaluations rather than solely focusing on a specific tumor site.