What Are the Rarest Cancers?

Cancer is a disease where the cells in parts of the body begin to divide extremely quickly and abnormally. When cells clump together into a lump, this is what is called a tumour. These abnormal cells can spread locally and cause damage or spread to other parts of the body and begin dividing abnormally in other organs in the body. Once cancer has spread to other parts of the body, it is called metastatic cancer or Stage 4 cancer and is at an advanced stage of the disease.

Clearly, the sooner the cancer is diagnosed, and the less chance that it has had to spread, the better the chances of survival. Some cancers are extremely common and doctors have a lot of knowledge about the disease, how it progresses and what the best treatments are for it. But, there are also a number of rare cancers that affect a small number of people worldwide every year.

What Is a 'Rare' Cancer?

A rare cancer is defined as occurring in fewer than 6 out of 100,000 people. Different organs have a greater chance of developing cancer than others. There are also different kinds of cancers of the same organ, that may be rarer than others within the same organ.

The medical profession understands cancer through clinical trials and experience, and the disadvantage of rare cancer types is that far less research has been done on them so less is known about them. This makes them often difficult to prevent, diagnose and even treat. Often, because they are so rare, pharmaceutical companies have not thought it worthwhile or profitable to research treatments, which results in fewer treatment options available to patients when diagnosed.

What Types of Cancer Are the Rarest? 

• Hyalinising Clear Cell Carcinoma: One of the rarest types of cancer is known as hyalinising clear cell carcinoma of the minor salivary gland. There have only been about 50 known cases. It affects the salivary glands, the tongue and the palate and results in swelling and difficulty swallowing. The good news is that it is treatable with surgery and has an extremely high survival rate. It is also more common in women than men. 
• Heart Cancer: There are about one or two cases a year. Heart cancer can cause an irregular heart beat and can lead to heart failure. It has a 17% 5-year survival rate which means that only 17 out of 100 people will survive the cancer by the end of 5 years. 
• Oesophageal Cancer: This is cancer of the tube that connects one’s pharynx (behind the mouth) to one’s stomach. Some cancers are rare in certain parts of the world and not others. Oesophageal cancer for example, is considered rare in the United States but is common in many parts of Southern Africa and India. 
• Chronic Myeloid Leukaemia (CML): With this cancer, the bone marrow makes abnormally high amounts of blood cells.  

• Childhood Acute Lymphoblastic Leukeamia: This rare blood cancer affects children and occurs when the bone marrow makes abnormally high amounts of white blood cells. 
• Wilm’s Tumour: this cancer mostly affects children, and is a cancer that grows in usually one (but can be both) kidney. It is very treatable and the outcome for the child is usually very positive. The 5-year survival rate is around 90%. 
• Anal Cancer: This is another uncommon cancer that occurs when abnormal cells grow in and around the anus which is the part of the body where the stools leave the rectum. It will present with pain or itching and often passing blood with the stools. It can be treated. 
• Merkel Cell Carcinoma: This is a skin cancer most usually appearing on the face, head or neck as painless, shiny lumps of the skin – often reddish or pink in colour. It has a good survival rate especially if diagnosed early – the 10-year survival rate is about 70%. 
• Thymic Carcinoma: The thymus is part of your lymphatic system which helps the body to fight off illnesses. Cancer can develop in this gland which is situated just behind the breastbone. It presents as a persistent cough, shortness of breath, chest pain, a hoarse voice and swelling in the neck. It is treatable with a 5-year survival rate of between 20-50% 

• Hepatoblastoma: This is a rare cancer that forms in the liver. It presents with pain or swelling in the abdominal area and also loss of appetite and weight loss. It is treatable and the 5-year survival rate is good – around 81%. 
• Glioblastoma: A form of brain cancer. It affects up to 5 people per 100,000 and causes nausea, headaches, memory problems, difficulty balancing and visual problems. It is treatable, but unfortunately has a very low survival rate. Most people live less than a year after it is diagnosed. 
• Ewings Sarcoma: This is a very rare cancer, affecting about 3 people in a million. It affects the bone or soft tissue of the pelvis, the thigh bone, the upper arm bone the ribs and the jaw. It can also be found in the collar bone. It presents as a lump close to the skin and bone pain or broken bones with no injury to cause it. It also presents with weight loss. It has a good 5-year survival rate of 70%, but this drops to 30% if it has spread to other parts of the body. 
• Male Breast Cancer: This presents similarly to that of female breast cancer. There is a thickening of breast tissue along with redness or sores on nipple area and the nipple may be painful and pulled inwards, with a discharge. It is treatable too. 
• Fibrosarcoma: A very rare cancer affecting about 5 people in a million. It is a soft tissue cancer that arises from fibrous tissue which is what holds the body’s bones, muscles and other organs in place. It presents with weight loss and an unusual swelling, possibly also a painful swollen lump. It is treatable.  

• Kaposi’s Sarcoma: Appears most commonly in people with HIV/AIDS. It affects the skin, mouth and sometimes internal organs. On the skin, it often appears as purple blotches.  

What Can I Do If I Get a Rare Form of Cancer? 

Getting a cancer diagnosis is hard for anyone. But, getting a rare cancer diagnosis can also cause additional anxiety because as described above, less is often known about rare cancers and there may be fewer treatment options available. There may be only a few experts who are able to treat the cancer and that may mean the patient needs to travel some distance to get help. Speak to your health professional to get the best possible treatment. Many people also find comfort in support groups where they can share their experiences and learn from others who are going through a similar journey.