There are many cancers out there that nearly everyone is familiar with, whether they’ve simply heard of them, had a family member face them, or even battled them personally.
Additionally, there are super rare cancers that many people have never heard of. These cancers are so uncommon that most clinicians only see a handful of cases in their careers. Also, these cancers present special challenges, such as being hard to diagnose, having limited clinical trial data, and requiring specialized care.
Below we explain several of the rarest tumor types, give context about how uncommon they are, and outline why specialized care matters.
What Counts as a Super Rare Cancer?
There is no single universal threshold, but many experts classify cancers with incidence measured in single digits per million, or a few hundred cases per year, as super rare cancers. The U.S. Rare Diseases Act defines rare diseases as conditions that affect fewer than 200,000 people in the United States. Within that group, super rare cancers are those that occur at rates far below even that threshold.
Examples of Super Rare Cancers and How Often They Occur
Uveal melanoma
Uveal melanoma is a cancer that arises from the pigment cells of the eye. It is much less common than skin melanoma. In the United States the age-adjusted incidence is approximately 5 to 6 cases per million people per year, which places it among super rare cancers. Diagnosis and treatment require ophthalmic oncology experts because the disease behaves differently than cutaneous melanoma does.
Merkel cell carcinoma
Merkel cell carcinoma is an aggressive skin cancer that remains uncommon. About 3,000 people in the United States are diagnosed each year. That low annual case count categorizes it as one of the rarest cancers, though its incidence has been rising and it is more frequently recognized now than in decades past. Management typically involves dermatologic oncology, surgical specialists, and systemic therapy from medical oncology.
Thymus cancers
Tumors of the thymus, including thymomas and thymic carcinomas, occur at roughly 1.3 cases per million people per year in the U.S. This is about 400 cases annually. These tumors are both rare and heterogeneous, so treatment is best coordinated at centers experienced with mediastinal tumors. Thymic cancers fit the definition of super rare cancers because of their very low incidence.
Chordoma
Chordoma is a rare tumor that arises from remnants of the notochord along the spine and skull base. In the United States the annual incidence is approximately 0.088 cases per 100,000 people. Because chordomas usually occur at critical anatomic sites, care requires experienced spine surgeons, skull base surgeons, radiation oncologists, and a multidisciplinary team. Chordoma is classically cited among super rare cancers.
Primary cardiac sarcoma and other heart tumors
Primary tumors of the heart are extremely uncommon. Cardiac sarcomas and other primary cardiac neoplasms occur at very low rates and are often reported as only a few hundred cases over many years across large registries. These tumors are among the rarest solid tumors and are therefore considered super rare cancers. Specialized cardiothoracic oncology teams and high-volume centers are essential for evaluation and treatment planning.
Other examples
Other super rare cancers include small cell carcinoma of the ovary, hypercalcemic types, esthesioneuroblastoma (also known as olfactory neuroblastoma), angiosarcoma, and rare pediatric and adult sarcomas. Each of these conditions may affect only dozens to a few hundred people per year in a large country.
Why Prevalence Matters for Patients
Low incidence affects everything from diagnosis to treatment options. Because super rare cancers are seen infrequently, they are more likely to be misdiagnosed or diagnosed late. There are often no large randomized trials to define a single best treatment. Instead, oncologists rely on registries, case series, expert consensus, and specialized clinical trials. For patients this means care at a center with lots of experience, because diagnosis improves the chances of accessing the right surgery, radiation technique, targeted therapy, or clinical trial.
Practical Advice for Those Diagnosed with a Super Rare Cancer
- Seek a second opinion at a specialty center or an academic medical center with experience in the specific tumor type.
- Ask about molecular profiling or genomic testing when appropriate. Some rare tumors have targetable mutations.
- Request pathology review by a specialist pathologist with experience in rare tumors. Correct classification is critical.
- Inquire about clinical trials or registry studies. Trials for super rare cancers may be open internationally and can offer access to novel therapies.
- Coordinate care with a multidisciplinary team including surgical oncology, medical oncology, radiation oncology, pathology, radiology, and supportive services.
Treating Rare Cancers at the Cancer Center for Healing in Irvine, CA
We understand the unique needs of patients facing super rare cancers in Irvine. If you have questions about an unusual diagnosis or need help finding an expert pathology review, please reach out to our comprehensive cancer program experienced with rare tumors. We also provide specialty clinical trials, accurate diagnosis, and access to advanced care to make a measurable difference when dealing with super rare cancers.
Get connected with us today and see what difference we can make in your story.
