Paraneoplastic syndromes are rare disorders that people can develop as a side effect of cancerous tumors (neoplasms). These syndromes can occur with many cancers, including breast cancer.

Understanding the connection between paraneoplastic syndromes and breast cancer is important. Having a paraneoplastic syndrome can worsen cancer prognosis, particularly if the syndrome is ignored or untreated.

What Are Paraneoplastic Syndromes?

Paraneoplastic syndromes are disorders caused by abnormal immune system responses to tumors. In general, paraneoplastic syndromes are caused by the body’s immune system attacking itself.

Although the causes of paraneoplastic syndromes are similar, the syndromes can manifest as many types of diseases. They can affect many parts of the body, such as the nervous system (brain, spinal cord, and nerves), endocrine system (hormones), blood, skin, and joints.

General Symptoms of Paraneoplastic Syndromes

Many symptoms and side effects are associated with paraneoplastic syndromes. These can include:

• Fever
• Night sweats
• Weight loss
• Loss of appetite
• High blood pressure
• Dizziness
• Difficulty with speech
• Weakness
• Weight gain
• Double vision
• Loss of coordination or sensation
• Slower reflexes
• Skin discoloration
• Benign (noncancerous) skin growths
• Itching
• Neuropathy (damage to nerves)

How Prevalent Are Paraneoplastic Syndromes?

Paraneoplastic syndromes develop in approximately 20 percent of people who have cancer. The syndromes occur most often in people who are middle-aged and have lung, ovarian, breast, or lymphatic cancer.

However, prevalence rates may be much lower for individual paraneoplastic syndrome types. For instance, paraneoplastic neurological syndromes occur in less than 1 percent of people with breast cancer. Because the individual prevalence rates are so rare, there is little available scientific research on how frequently these syndromes occur.

Paraneoplastic Syndromes in Breast Cancer

Many types of paraneoplastic syndromes can occur during the course of breast cancer. For instance, among paraneoplastic neurological syndromes, the following diseases have been associated with breast cancer:

• Sensory-type neuropathy — Damage to the body’s sensory nerves, which transmit sensations such as touch, pain, and temperature
• Motor-type neuropathy — Damage to the body’s motor (or movement) nerve cells
• Paraneoplastic cerebellar degeneration — Deterioration of a brain region known as the cerebellum, which causes symptoms like double vision, an unsteady gait, and trouble with fine hand movements
• Opsoclonus-myoclonus syndrome — A disease that affects the nervous system and causes fast, multidirectional eye movements; sudden, involuntary muscle spasms; irritability; problems with sleep; and uncoordinated movement
• Stiff-person syndrome — A disorder characterized by muscle rigidity and spasms with heightened sensitivity to things like noise, emotions, and touch
• Encephalomyelitis — Inflammation of the brain and spinal cord that damages the myelin (fatty layer of insulation) that surrounds nerve fibers. Encephalomyelitis of the limbic system (emotions system) has been particularly linked to neuroendocrine breast cancer.
• Paraneoplastic retinopathy — Damage to the body’s retinal (vision) system

Neurological syndromes are not the only paraneoplastic syndromes associated with breast cancer. One study observed stiff-person syndrome and transverse myelitis (inflammation of a section of the spinal cord), plus the non-neurological syndrome diabetes insipidus (a disorder that causes an imbalance of fluids in the body, excessive thirst, and frequent urination).

Treatment and Prognosis of Paraneoplastic Syndromes

Prompt diagnosis and treatment of paraneoplastic syndromes is important because paraneoplastic syndromes can affect clinical outcomes for breast cancer. Sometimes, people may notice the symptoms of a paraneoplastic syndrome before they notice any symptoms of breast cancer.

Paraneoplastic syndromes can be treated in many ways, such as treating the underlying cancer itself. Other treatment options will vary depending on the type of syndrome and the part of the body affected.

Because these syndromes are related to inflammation and the autoimmune system, treatment options can include:

• Corticosteroids, which reduce inflammation
• Intravenous immunoglobulins, which boost healthy antibodies
• Immunosuppressants, which manage the immune system’s response
• Plasmapheresis, which reduces the amount of antibodies in the blood
• Speech and physical therapy, which help people speak and move better

As paraneoplastic syndromes vary from person to person, the prognosis of these syndromes will also vary. In some cases, symptoms can be easily managed. In other cases, the symptoms can be life-threatening.

Because the presence of paraneoplastic syndromes can make the prognosis of the underlying cancer worse, it is important to recognize paraneoplastic syndromes when they occur. If you are experiencing new or unusual symptoms, talk to your doctor immediately.

Talk With Others Who Understand

MyBCTeam is the social network for people with breast cancer and their loved ones. On MyBCTeam, members come together to ask questions, give advice, and share their stories with others who understand life with breast cancer.

Do you or a loved one have paraneoplastic syndromes and breast cancer? Share your experiences in the comments below, or start a conversation by posting on MyBCTeam.