It can be hard to diagnose histiocytosis. There are many symptoms, and several other health conditions can also cause the same symptoms.

It’s also very rare, so many doctors do not know the signs of histiocytosis. For this reason, it can take a long time to get a diagnosis for histiocytosis.

MSK has experts who know the symptoms of histiocytosis and can make a correct diagnosis.

Learn more about how MSK diagnoses cancer and other conditions.

Imaging Scans

Imaging tests are often used to find which areas are affected by histiocytosis. You can learn more about the role of imaging in diagnosing cancer and other conditions.

• CT (computed tomography) scans make 3D images of areas inside your body. The images are most helpful for showing histiocytosis in the lungs, heart, kidneys, lymph nodes, and other organs. CT scans are sometimes called CAT scans.
• MRI scans make detailed 3D images of areas inside your body. Most people with histiocytosis have an MRI of their brain and pituitary gland. We also may take images of other areas, such as the heart or belly.
• X-rays  let us see an area inside your body. They’re the oldest and most common type of medical imaging scan. With children, we often take an X-ray of all the bones in the body, called a skeletal survey. This lets us check for bone lesions that may not cause any symptoms.
• Ultrasound images of the liver and spleen are often taken in children to look for signs of histiocytosis. An ultrasound uses high-frequency sound waves to make still or moving pictures of areas in your body.
• Positron emission tomography (PET) scans are a type of nuclear medicine scan. They show how much glucose (sugar) is used in different areas of your body. A PET scan can help us find cancer cells by showing areas that are using more glucose than normal. We may use a PET scan to get information about tumors and the location of histiocytosis.

Breathing and Blood Tests

The type of test depends on the kind of histiocytosis and your symptoms.

Some people with histiocytosis have breathing problems. A pulmonary function test measures how well you can breathe. It can be helpful to diagnose histiocytosis.

Doctors may order blood tests to measure:

• Hormone function
• How the kidneys and liver are working
• Blood cell counts
• Inflammation  

These tests can also tell us about the type of histiocytosis you have.

Tumor tissue biopsy and genetic testing

Some treatments for histiocytosis target a genetic change (mutation or variant). Doctors often test the molecules in a tumor tissue sample for the genes we know are involved in histiocytosis. We get these tissue samples during a biopsy procedure.

For example, about half of people with Erdheim-Chester disease and Langerhans cell histiocytosis have BRAF genetic mutations in their tumors. There are drugs that target BRAF mutations.

Genetic testing for histiocytosis

There are several ways to test histiocytosis tissue for gene mutations. We can look for genetic changes in tumor tissue and in blood samples.

Tumor genetic testing

MSK examines histiocytosis gene mutations using an advanced tumor tissue test. This test was developed at MSK and is called MSK-IMPACT^®. The results of this test can help doctors match people with the best treatments for histiocytosis.

Genetic blood tests

If we are not able to diagnose histiocytosis from a tumor sample, we may use MSK-ACCESS^®. It’s a test we also use when there’s is not enough tissue to examine.

This liquid biopsy is a type of blood test. It lets us look for 129 key genes linked to cancer. It’s a way to find the genetic profile of tumors. We can also monitor (watch) whether a disease is getting better, worse, or staying the same.