Diagnosing histiocytosis can be challenging because the condition is rare. In addition, the symptoms vary and may be common to many different disorders.

Many doctors are not familiar with the symptoms of histiocytosis. For this reason, it can take a long time to get a diagnosis.

To receive a diagnosis of histiocytosis, you may have some or all of the following tests.

Radiology Scans

CT scans can identify areas of histiocytosis. They can be used to look at any part of the body, but CT is most helpful for detecting histiocytosis in the lungs, heart, kidneys, lymph nodes, and other organs.

MRI scans can get a very detailed picture of certain organs. Most people with histiocytosis have an MRI of their brain and pituitary gland. MRIs examining other areas of the body — the heart or abdomen, for example — may be used as well.

In children, doctors usually do X-rays of all the bones in the body. This is called a skeleton survey. This survey allows doctors to check for bone lesions that may not have caused symptoms.

An ultrasound of the liver and spleen are often taken for children. These are used to look for signs of involvement by the histiocytosis.

Blood and Breathing Tests

Some people with histiocytosis have breathing problems. A pulmonary function test looks at different aspects of breathing. These tests can be helpful when diagnosing some cases of histiocytosis.

Depending on the histiocytosis diagnosis and particular symptoms, doctors may do different blood tests. These tests can evaluate hormone function, kidney and liver function, blood cell counts, and inflammation within the body.

Once a diagnosis is made, these tests may also be used to learn more about the specific disease.

Tissue Biopsy and Molecular Testing

Because some treatments for histiocytosis target particular mutations, doctors may perform molecular testing of tissue samples. These samples are obtained by doing a biopsy.

When a biopsy is performed, a small piece of tissue is removed. These tissue samples may be obtained using small needles. In other cases, removal may require more extensive procedures, like surgery. A pathologist then examines the tissue to make a diagnosis.

A biopsy is extremely important for diagnosing histiocytosis. Histiocytosis biopsies can be very complicated to evaluate. Therefore, it is vital that samples are reviewed by pathologists who have experience diagnosing these conditions. Frequently, people with histiocytosis undergo several biopsies before they receive a confirmed diagnosis.

Testing biopsy material for gene mutations is an important part of evaluating histiocytosis. About half of people with Erdheim-Chester disease and Langerhans cell histiocytosis have a mutation in a gene called BRAF in their tumor. This gene mutation can be targeted with drugs.

There are many ways to test histiocytosis tissue for gene mutations. At MSK, tumor genes are evaluated with a test called MSK-IMPACT™. This test identifies the gene mutations relevant to histiocytosis. Data from the test can help match people with histiocytosis to the appropriate therapies.