Sarcoma vs. Carcinoma: Differences and Similarities

There are a number of differences between sarcomas and carcinomas, though individual cancers within each category can vary tremendously. Carcinomas account for the majority of cancers with only 1% of cancers in adults being sarcomas. In children, however, sarcomas account for over 15% of cancers, making research critical. Carcinomas arise out of epithelial cells that line the surface and organs of the body, whereas sarcomas arise from connective tissues such as bone, cartilage, fibrous tissue, blood vessels, and nerves. Learn about the similarities and differences with regard to subtypes, symptoms, causes, diagnosis, treatments, and prognosis.

Similarities Between Sarcomas and Carcinomas

There are many differences between sarcomas and carcinomas, so it is helpful to begin by talking about the similarities. Some of these include:

• Both are cancer (malignant): There are a number of differences between malignant tumors and benign tumors, with a major difference being that malignant tumors can spread to distant regions of the body.
• Both can be relatively treatable or life-threatening: Low-grade sarcomas and some carcinomas such as basal cell carcinoma of the skin can be very treatable. Likewise, some sarcomas as well as some carcinomas (for example, pancreatic cancer) are very challenging to treat with saddening five-year survival rates.
• Both can occur at any age: While sarcomas are more commonly found in young people, both sarcomas and carcinomas may be diagnosed at any age.
• With both, the cause is often unknown: While certain genetic syndromes as well as exposures may be associated with both sarcomas and carcinomas, the exact cause of either type of cancer is often unknown.
• Both can be difficult to diagnose: Both sarcomas and carcinomas may be misdiagnosed at first.
• Both require people to be their own advocates: With both sarcomas and uncommon types of carcinomas, finding physicians who specialize in these rare or uncommon cancers may improve outcomes.

Basic Differences

There are also many differences between sarcomas and carcinomas. Carcinomas are much more common, accounting for 85% to 90% of cancers. Sarcomas, in contrast, represent slightly less than 1% of cancer types. (The other types of cancer include leukemias, lymphomas, and myelomas, although some cancers may have characteristics of more than one type, for example, carcinosarcomas.)

Origin/Cell Types

During in utero development of the embryo (embryogenesis), differentiation (the process of different tissues being formed) begins with the formation of three germ layers. These include the:

• Ectoderm: The layer which eventually becomes the skin and mucous membranes of the nose, the lining of organs, and nerve tissue
• Mesoderm: The layer which differentiates into connective tissue, lining of the lungs (pleura), heart (pericardium), and abdomen (peritoneum), and blood cells
• Endoderm: The layer which forms the lining of the gastrointestinal tract, the lower respiratory tract, and more

Sarcomas begin in cells known as mesenchymal cells, often derived from the mesoderm, whereas carcinomas begin in epithelial cells; cells derived from the ectoderm and endoderm and that line the inside and outside surfaces of the body. That said, there are some exceptions. For example, the epithelial cells on the inner surface of the uterus (endometrium), bladder, and vagina are derived from the mesoderm.

Tissues

Carcinomas arise in tissues that line the body cavities or the skin, for example, the airways of the lung and the milk ducts of the breast. Sarcomas arise in tissues referred to as connective tissue, including bone, cartilage, fat, nerves, muscles, ligaments, tendons, nerves, and more. Sarcomas are often separated into two main categories; bone sarcomas that include tumors of bone, cartilage, and bone marrow, and soft tissue sarcomas.

Types and Subtypes of Carcinomas

Carcinomas are named according to the tissue in which they arise as well as the type of cells.

• Adenocarcinoma: Adenomatous cells are glandular cells that secrete substances such as mucus
• Squamous cell carcinoma: Squamous cells are flat cells found on surfaces, such as the outer layer of skin and lining of the upper esophagus
• Basal cell carcinoma: Basal cells are found in the deepest layer of skin
• Transitional cell carcinoma: Transitional cells are cells that stretch and are found in areas such as the bladder

Different subtypes may occur in different regions of the same organ, for example, non-small cell lung cancers may be squamous cell carcinomas of the lung or lung adenocarcinomas. Similarly, esophageal cancers may arise in squamous cells (squamous cell carcinomas) or glandular cells (adenocarcinomas).

Common carcinomas include lung adenocarcinoma, colon adenocarcinoma, squamous cell carcinomas of the head and neck, bladder cancer (most often a transitional cell carcinoma), and basal cell carcinomas of the skin.

Tissue Types and Subtypes of Sarcomas

Unlike carcinomas, there are over 50 different subtypes of sarcomas. Examples of sarcoma based on tissue type include:

• Bone (osteosarcoma or osteogenic sarcoma)
• Fat (adipose tissue): liposarcoma
• Cartilage: chondrosarcoma
• Smooth muscle (such as in the uterus): leiomyosarcoma
• Skeletal muscle: rhabdomyosarcoma
• Fibrous tissue: fibrosarcoma
• Joint lining: synovial sarcoma
• Blood vessels: angiosarcoma, when lymph vessels are involved, these tumors are referred to as lymphoangiosarcomas
• Mesothelium: mesothelioma (these tumors may involve the pleura (mesothelium around the lungs), pericardium (membranes around the heart) or peritoneum (membranes around the abdomen).
• Nerves: neuroblastoma, medulloblastoma
• Cells surrounding nerves: neurofibrosarcomas, malignant Schwammomas
• Connective tissue in the brain: glioma, astrocytoma
• Digestive tract: gastrointestinal stromal tumors (GISTs)
• Primitive embryonic tissue: myxosarcoma
• Combination of cell types: undifferentiated pleomorphic sarcoma (previously called malignant fibrous histiocytoma)

The most common sarcomas in childhood are rhabdomyosarcomas. In adults, the most common sarcomas are soft tissue sarcomas, including undifferentiated pleomorphic sarcoma, liposarcomas, and leiomyosarcomas.

Overlap Between Sarcomas and Carcinomas

The region of the body does not always distinguish sarcomas and carcinomas. For example, breast sarcomas (that account for less than 1% of breast cancers) arise in the connective tissue of the breasts rather than milk ducts or lobules. Most "colon cancers" are adenocarcinomas, but 1% to 2% of tumors in this region are leiomyosarcomas of the colon and rectum.

Some tumors may have characteristics of both carcinomas and sarcomas and may be referred to as carcinosarcomas or sarcomatoid carcinomas.

Cancer Terminology: Oma vs. Sarcoma Etc.

Most of the time (but not always), the description of a tumor differentiates benign connective tissue tumors from malignant sarcomas.

For example, a lipoma is a benign tumor of fat (adipose tissue), and a liposarcoma is a cancerous tumor of the tissue. A hemangioma is a benign tumor of blood vessels, whereas a hemangiosarcoma is a malignant tumor.

There are exceptions in this classification as well. For example, a chordoma (tumor of the nuchal cord) is malignant. A glioma is a cancer (not benign tumor) of glial cells in the brain. Sometimes, the word malignant is used to distinguish benign and malignant tumors. For example, a meningioma refers to a benign tumor of the meninges (membranes lining the brain), whereas a cancerous tumor is referred to as malignant meningioma.

Signs and Symptoms

Carcinomas may declare themselves with a number of symptoms often related to the organ in which they arise. For example, lung cancer may present with a cough or shortness of breath, breast cancer may present with a breast lump, and pancreatic cancer may present with jaundice, though not usually until the disease is very advanced.

Sarcomas can likewise present with different symptoms. Sarcomas that arise in the arms and legs often present as a mass that can be painful or painless. When pain is present, it is often worst at night. Sarcomas in bone (osteosarcomas) may present with bone pain or swelling over or near bones. In some cases, the condition is only diagnosed after a fracture occurs (pathologic fracture) through an area of bone that has been weakened by the tumor. With Ewing sarcoma, the swelling or lump often feels warm and may be associated with a fever. Sarcomas of the digestive tract (GI stromal tumors) may have symptoms similar to colon carcinoma such as blood in the stool, abdominal pain, or weight loss.

Causes and Risk Factors

The major risk factors for carcinomas are fairly well known, and include lifestyle factors (such as smoking, obesity, and sedentary behavior), radiation (including ultraviolet radiation), genetics, age, viral infections, and environmental exposures among others.

In most cases with sarcomas, identifiable risk factors aren't present, and these tumors have not been found to be associated with smoking, obesity, diet, or lack of exercise. Risk factors for sarcomas may include:

• Radiation, such as radiation therapy, as well as some types of chemotherapy drugs (Cancers that develop due to the carcinogenic properties of prior cancer treatments are referred to as secondary cancers)
• Environmental exposures, including exposure to vinyl chloride, some herbicides, arsenic, and thorium dioxide
• HIV infection (a risk factor for Kaposi's sarcoma)
• Uncommon genetic syndromes such as neurofibromatosis, Li-Fraumeni syndrome, Werner syndrome, Gorlin syndrome, Costello syndrome, Bloom syndrome, Diamond-Blackfan syndrome, Noonan syndrome, Beckwith-Wiedermann syndrome, tuberous sclerosis, familial adenomatous polyposis

Some sarcomas are associated with certain developmental time periods. For example, osteosarcomas are most common during bone growth between the ages of 10 and 20.

With some sarcomas, risk factors have been identified and studied to a greater extent. For example, angiosarcoma of the breast has been associated with chronic lymphedema, radiation therapy for breast cancer, and a particular type of breast implants (that have now been withdrawn from the market). Mesothelioma is strongly associated with asbestos exposure.

Rhabdomyosarcomas in children have also been associated with parental use of cocaine and marijuana. Few risk factors have been identified at this time for Ewing sarcoma, though these cancers appear to be more common among children who have had hernias.

Diagnosis, Screening, and Staging

The diagnostic process for sarcomas can be similar to carcinomas, and often begins with scans (such as a CT scan, MRI, bone scan, or PET scan), or in the case of digestive tract sarcomas, endoscopy. Similarly, a biopsy is needed to determine the type of cancer as well as the tumor grade (the aggressiveness of the cancer). Special stains may likewise be helpful.

As with carcinomas, DNA testing (such as next-generation sequencing) is often helpful, but in the case of some sarcomas, RNA testing may be helpful as well.

Screening

Unlike carcinomas such as breast cancer, lung cancer, and colon cancer, general screening tests are not currently available for sarcomas.

Precancerous Phase vs. No Precancerous Phase

With carcinomas, tumors can sometimes be detected before they are invasive (before they extend through something known as the basement membrane). These precancerous tumors are non-invasive and are referred to as carcinoma in situ or stage 0 cancer. For example, when stage 0 lung cancer is detected it may be treated before it has the opportunity to become invasive and potentially spread. In contrast, once a sarcoma is detected it is considered invasive.

Staging

There are also differences in staging methods due to the way in which carcinomas and sarcomas often spread.

TNM staging with carcinomas looks at the size of a tumor (T), the presence or absence of tumor cells in lymph nodes (N), and the presence or absence of metastases. Carcinomas often spread first to lymph nodes, but this spread does not mean the carcinoma is metastastic. In fact, cancers such as stage 2 breast cancer may have spread to lymph nodes.

Sarcomas usually spread via the bloodstream and much less often through the lymphatic system. For this reason, they are less likely to spread to lymph nodes, and when they do spread, are more likely to be found in another organ (such as the lungs). With staging of sarcomas, the tumor grade (aggressiveness of the cancer cells) is often more important.

Tumor Grade

The behavior, treatment, and prognosis of sarcomas relate strongly to their tumor grade.

Behavior

Carcinomas and sarcomas can behave differently with how they grow and spread. Carcinomas tend to grow and invade nearby structures, and in fact, the derivation of the word cancer from the word "crab" refers to these fingerlike projections or spicules that invade other structures. These cancers can spread locally in this way, via the lymphatic system, the bloodstream, and in the case of lung cancer, through the airways (aerogenous metastases).

Sarcomas often grow as more of a ball, pushing structures (such as nerves and blood vessels) out of their way rather than invading them. They spread primarily through the bloodstream, with the most common site of metastasis being the lungs.

Treatment Options

In general, sarcomas can be more challenging to treat both in having fewer options available, and due to the fact that surgery (such as amputations in children) can be very disfiguring. Newer treatments, however, are becoming available such as targeted therapies and limb-sparing surgery.

Surgery

Surgery is often the treatment of choice for sarcomas as well as early stage carcinomas. Newer limb-sparing techniques have been developed for children with sarcomas, and the use of targeted therapies (see below) has in some cases reduced the size of a sarcoma prior to surgery so that much less extensive surgery is possible.

Radiation Therapy

Radiation therapy is commonly used with both sarcomas and carcinomas.

Chemotherapy

Many sarcomas are less responsive to chemotherapy than carcinomas, but this varies, for example, rhabdomyosarcomas in children tend to respond well to chemotherapy.

Targeted Therapy

Targeted therapies, or treatments that target specific abnormalities in the growth of cancer cells, have made a significant difference in the treatment of carcinomas such as some breast cancers and non-small cell lung cancers. These drugs are making a difference in the treatment of some sarcomas as well. In 2018, the drug Vitrakvi (larotrectinib) was approved for cancers, regardless of type, that harbor a NTRK fusion gene. This includes roughly 1% of solid tumors (such as colon cancer, lung cancer, and breast cancer) but up to 60% of some sarcomas, such as infantile fibrosarcoma.

As a treatment that can target both sarcomas and carcinomas, Vitrakvi is an example of precision medicine, and how cancer treatment is changing such that it focuses on genetic abnormalities in the cancer cells rather than the cell type or tissue of origin.

Immunotherapy

Immunotherapy drugs such as checkpoint inhibitors have been a paradigm change in the treatment of some cancers, with sometimes drastic improvement in even very advanced metastatic carcinomas. Fortunately, these treatments are now being investigated for use in metastatic sarcoma as well, particularly undifferentiated pleomorphic sarcoma, myxofibrosarcoma, leiomyosarcoma, and angiosarcoma.

Prognosis

The prognosis of sarcomas and carcinomas depends strongly on the particular type of cancer, the aggressiveness of the tumor, age at diagnosis, and the stage at which they are diagnosed. For soft tissue sarcomas, the 5-year survival rate for localized tumors is 81%, which drops to 16% for metastatic tumors.

Summary of Differences

A Word From Verywell

There are a number of important differences between sarcomas and carcinomas, including treatment. That said, as our understanding of cancer improves and treatment focuses on treatment underlying genetic anomalies in the cancer cells, the distinction between the two categories of cancer types may become less important.