10 Rare Cancers – What You Should Know

Not every part of the human body has the same risk of developing cancer. Some organs and tissues develop fewer cancers than other parts of the body.

Cancer rates may also differ within an organ. For example, one type of pancreatic cancer may be common while another is rare.

The most common and rarest cancers are generally similar worldwide. For example, the 10 most common cancers in Turkey, in order, are lung, breast, prostate, thyroid, stomach, bladder, colon, rectum, pancreatic cancer, and leukemia. Each of these cancers affects more than 10 thousand people every year; for lung cancer, the figure was 41 thousand in 2020 (see Turkey Cancer Statistics 2020).

Each rare cancer affects fewer people; for example, fewer than 1000 patients annually in Turkey for each rare cancer. However, there are many different rare cancers; together, such rare cancers account for 27% of all cancer cases and 25% of cancer-related deaths.

1. Mesothelioma

Mesothelioma is a rare cancer that may remain undiagnosed or misdiagnosed for many years. About 3,000 people in the USA and around 500 in Turkey are diagnosed with mesothelioma each year. Although there is still no curative treatment for mesothelioma, which is often diagnosed at an advanced stage, advances in approaches such as chemotherapy, targeted treatments, immunotherapies, and electrotherapy are producing promising results.

Cancer of the membranes covering the lungs, heart, and abdominal organs is called malignant mesothelioma, or simply mesothelioma. Only 15% to 20% of patients diagnosed with pleural mesothelioma have early-stage disease and are suitable for surgery.

The most important cause of mesothelioma is asbestos dust. Asbestos is a natural material formerly used to insulate buildings. Preferred for its fire resistance, this material made of tiny fibers can cause mesothelioma and lung, laryngeal (voice box), and ovarian cancer when inhaled.

People with mesothelioma may have the following symptoms;

• Chest pain,
• Shortness of breath,
• Extreme fatigue,
• Fever and sweating, especially at night,
• Chronic cough,
• Loss of appetite and unexplained weight loss.
• Finger clubbing

Mesothelioma is known for an unfavorable course, and before immunotherapies its median overall survival was 14 months. With combination immunotherapy approved by the FDA in 2020, this exceeded 18 months.

2. Childhood Acute Lymphoblastic Leukemia

Childhood acute lymphoblastic leukemia (ALL) is one of the blood- and bone marrow-derived (hematological) cancers. Although rare, it is the most common cancer affecting children.

Symptoms may include;

• Fever
• Fatigue
• Easy bruising

Treatment options include;

• Combination treatment with two or more chemotherapy drugs
• Targeted therapy
• Stem cell transplantation, bone marrow transplantation

The 5-year survival rate for childhood ALL is approximately 90%.

3. Anal Cancer

Anal cancer occurs in the anus, the opening at the end of the rectum. It is much rarer than colon or rectal cancer. According to our statistics, approximately 233 new cases of anal cancer were detected in Turkey in 2020.

Symptoms may include;

• Rectal bleeding
• Itching
• A lump near the anus

Depending on the stage and location of the tumor, treatment may include;

• Surgery
• Chemotherapy
• Radiation therapy

The 5-year survival rate ranges from 82% for regional tumors to 34% for metastatic cancer.

4. Merkel Cell Carcinoma

Merkel cell carcinoma is a rare, aggressive type of skin cancer. It develops from skin cells called “Merkel” cells. Also known as Ranvier cells or tactile epithelial cells, Merkel cells are oval mechanoreceptors needed for light-touch sensation in the skin. Merkel cell cancer is a rare skin cancer with aggressive biology, mainly affecting older adults with fair skin and tending to recur regionally and metastasize to regional lymph nodes. Several other terms are used for this tumor, including neuroendocrine or primary small cell carcinoma of the skin, trabecular cell carcinoma, and anaplastic skin cancer.

According to US statistics, it occurs in approximately 1 in every 166,000 people. It is more common in men, with a median age at diagnosis of 74 for men and 76 for women. Identified risk factors include intense exposure to the sun’s UV rays, fair skin, infections that suppress the immune system or use of immunosuppressive medicines, and having secondary cancers. 81% of Merkel cell carcinoma lesions are found in sun-exposed areas.

The main sign of Merkel cell carcinoma is a lump developing on skin heavily exposed to sunlight. The lump may generally be;

• Painless
• Fast-growing
• Firm to the touch
• Dome-shaped or raised
• Redness or dark coloring around the lump

Standard treatment options may include;

• Surgery
• Chemotherapy
• Radiation therapy
• Immunotherapy

According to US statistics, the average 5-year survival rate across all stages of Merkel cell carcinoma is 63%.

5. Thymic Carcinoma

Thymic carcinoma is a cancer that can form in the outer cells of the thymus, a small organ in the upper chest that produces white blood cells. Thymic carcinoma cells grow rapidly and tend to spread to other parts of the body, such as the lungs.

Thymic carcinoma is generally very rare, with an estimated 50 or fewer new cases in Turkey each year and approximately 400 new cases annually in the USA.

Most people have no symptoms in the early stages of thymic carcinoma. However, the following may develop at later stages;

• Persistent cough
• Shortness of breath
• Chest pain
• Hoarse voice
• Swelling in the chest, face, neck, or arms

Treatment for thymic carcinoma may include a combination of:

• Surgery
• Chemotherapy
• Radiotherapy
• Hormone therapy
• Targeted therapy

According to the US National Cancer Institute, the 5-year survival rate for unresectable, locally advanced carcinoma is 36%. For carcinoma that has spread to other parts of the body, the rate is 24%.

6. Hepatoblastoma

Hepatoblastoma is a liver cancer that generally occurs in the first 3 years of life. According to the American Childhood Cancer Organization, 50-70 new cases are detected each year in the USA.

Symptoms vary among children and may include;

• Abdominal pain or swelling
• Loss of appetite
• Weight loss

Treatment options may include;

• Surgery
• Chemotherapy
• Liver transplantation
• Radiation therapy

A population-based study conducted in 2019 determined that the average 5-year survival rate for children with this disease was 81.5%.

7. Glioblastoma

Glioblastoma is an aggressive type of brain tumor, also called GBM or GBM-IV. Although it is the most common malignant primary brain tumor, each year in Turkey there are 5.4 new brain tumors in men and 4 in women per 100,000 people.

Symptoms depend on the tumor’s location and may include;

• Headache
• Nausea
• Memory loss

Although there is not yet a definitive treatment for this type of cancer, treatment options may include;

• Surgery
• Radiation therapy
• Chemotherapy
• A combination of any two of the above treatment options

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8. Ewing Sarcoma

Ewing sarcoma is a cancer that typically grows in bone tissue. It generally affects children and young adults, and approximately 2.93 children per 100,000 are diagnosed each year in the USA.

Symptoms of Ewing sarcoma may include;

• Pain and swelling near the affected area
• A lump
• Fever
• A bone breaking without a clear cause

Treatment options may include;

• Chemotherapy
• Radiation therapy
• Surgery
• High-dose chemotherapy with stem cell support

According to US statistics, the 5-year survival rate across all stages of Ewing sarcoma is 61%.

9. Kaposi Sarcoma

Kaposi sarcoma is cancer of the cells lining lymph or blood vessels and is a type of soft tissue sarcoma.

Kaposi sarcoma is most common in patients with untreated AIDS.

Kaposi sarcoma is a multicentric tumor that can range to multiple lesions involving one or more organs, particularly the mouth, digestive system, lymph nodes, lungs, and bones. Its subtypes are the classic, endemic, transplantation-associated, and AIDS-associated forms. The HHV8 virus causes all these forms.

HHV8 encodes a series of genes that trigger cell proliferation, cytokine production, and new blood vessel formation, thereby causing cancer. Kaposi sarcoma lesions develop most often on the legs because HHV8-encoded genes activated by factors triggered in this oxygen-poor area, compared with other parts of the body, facilitate tumor development.

Between 2009 and 2013, approximately 0.5 cases of Kaposi sarcoma per 100,000 people were observed annually in the USA.

The main sign of Kaposi sarcoma is the development of purple, red, or brown patches. These lesions may develop;

• On the skin, mostly on the legs or face
• In other organs of the body
• On the mucous membranes of the mouth, nose, and throat
• In lymph nodes

Treatment options may include;

• Radiation therapy
• Highly active antiretroviral therapy
• Surgery
• Cryosurgery
• Chemotherapy
• Immunotherapy
• Targeted drugs

The relative 5-year survival rate for Kaposi sarcoma is 73%.

- Related topic: FDA grants accelerated approval to pomalidomide for Kaposi sarcoma

10. Esophageal Cancer

Esophageal cancer is cancer of the esophagus, the tube carrying food and drinks from the throat to the stomach. According to Turkey Cancer Statistics 2020, approximately 1,405 people in Turkey were newly diagnosed with esophageal cancer in 2020.

This type of cancer accounts for 0.6% of cases diagnosed in 1 year in Turkey. However, it is more common in other countries, such as India, South Africa, Northern China, and Iran.

Symptoms may include;

• Heartburn/acid reflux/stomach discomfort
• Chronic cough
• Difficulty swallowing

Treatment options may include;

• Chemotherapy: Medicines that kill cancer cells.
• Radiation therapy (Radiotherapy): High doses of radiation to kill cancer cells.
• Surgery
• Immunotherapy
• Targeted therapy: Medicines that target cellular mechanisms enabling cancer cells to grow.

According to US statistics, the 5-year survival rate ranges from 47% for early and locally advanced tumors to 5% for metastatic cancer.

What Is Cancer?

The human body consists of trillions of cells that normally grow and multiply. When cells become abnormal or old, they die and are replaced by new cells.

Sometimes this process does not work as it should, and abnormal cells continue multiplying instead of dying. These cells can form masses or tumors that are benign, meaning noncancerous, or malignant, meaning cancerous. If cancerous, they may grow and spread to nearby tissues and reach distant parts of the body, also known as metastasis.

Once cancer becomes large enough, it may affect normal body functioning, leading to symptoms.

Cancer is the second-leading cause of death worldwide. In 2020, 19.3 million new cancer cases were reported globally, and the number of new cases arising annually is estimated to increase by 47% by 2040. However, improvements in treatments and public awareness should not be overlooked: cancer-related deaths in the USA, for example, fell by 27% between 1999 and 2019.

Why Are Some Cancers Rarer Than Others?

The rarity of cancers is a complex issue, and there is currently no universal definition of a rare cancer.

A particular type of cancer may be rare because it tends to occur more often in some populations than in others. Some cancers may be considered rare because they are harder to diagnose accurately. The frequency of particular cancers may also vary greatly by geographical location.

A review prepared in 2015 showed that cancer occurs more often in some body tissues than in others. Some differences result from inherited genes, while others arise from environmental factors such as smoking or alcohol use. Nevertheless, these factors do not fully explain the variation in rates among cancers.

The review’s researchers suggested that the main factor controlling a tissue’s likelihood of developing cancer is the lifetime number of stem cell divisions within it. In other words, the more a cell divides, the greater its long-term likelihood of becoming cancerous; the cumulative effects of environmental carcinogens in these tissues also influence this risk, of course. This is why most cancers occur at older ages.

According to the concept underlying this theory, genetic changes occur randomly during stem cell divisions called DNA replication. These genetic changes point to a strong correlation between the lifetime number of stem cell divisions in a tissue and lifetime cancer risk.

Research into rare cancers receives less financial and scientific support than research into more common cancers, which is one reason for the considerable uncertainty surrounding them.

Summary

Like common cancers, rare cancers can occur in many parts of the body. They can also affect children as well as adults.

Symptoms of rare cancers may vary greatly depending on the organs and tissues affected. Treatment options generally include surgery, chemotherapy, and radiation, although patients may sometimes benefit from additional treatments such as immunotherapy or targeted drugs.

Outcomes may differ for patients with rare cancers, but early diagnosis can make a substantial difference to survival rates for some cancers.