This is a medical question of type : exams and tests 
 How to diagnose Langerhans Cell Histiocytosis ? 
 The following tests and procedures may be used to detect (find) and diagnose LCH or conditions caused by LCH:         -   Physical exam and history : An exam of the body to check general signs of health, including checking for signs of disease, such as lumps or anything else that seems unusual. A history of the patient's health habits and past illnesses and treatments will also be taken.    -   Neurological exam : A series of questions and tests to check the brain, spinal cord, and nerve function. The exam checks a person's mental status, coordination, and ability to walk normally, and how well the muscles, senses, and reflexes work. This may also be called a neuro exam or a neurologic exam.     -   Complete blood count (CBC) with differential : A procedure in which a sample of blood is drawn and checked for the following:               - The amount of hemoglobin (the protein that carries oxygen) in the red blood cells.      -  The portion of the blood sample made up of red blood cells.       - The number and type of white blood cells.      - The number of red blood cells and platelets.             -   Blood chemistry studies : A procedure in which a blood sample is checked to measure the amounts of certain substances released into the body by organs and tissues in the body. An unusual (higher or lower than normal) amount of a substance can be a sign of disease.    -   Liver function test : A blood test to measure the blood levels of certain substances released by the liver. A high or low level of these substances can be a sign of disease in the liver.    -   BRAF gene testing : A laboratory test in which a sample of blood or tissue is tested for mutations of the BRAF gene.    -   Urinalysis : A test to check the color of urine and its contents, such as sugar, protein, red blood cells, and white blood cells.     -   Water deprivation test : A test to check how much urine is made and whether it becomes concentrated when little or no water is given. This test is used to diagnose diabetes insipidus, which may be caused by LCH.    -   Bone marrow aspiration and biopsy : The removal of bone marrow and a small piece of bone by inserting a hollow needle into the hipbone. A pathologist views the bone marrow and bone under a microscope to look for signs of LCH.  The following tests may be done on the tissue that was removed:               -  Immunohistochemistry : A test that uses antibodies to check for certain antigens in a sample of tissue. The antibody is usually linked to a radioactive substance or a dye that causes the tissue to light up under a microscope. This type of test may be used to tell the difference between different types of cancer.       -  Flow cytometry : A laboratory test that measures the number of cells in a sample, how many cells are live, and the size of the cells. It also shows the shapes of the cells and whether there are tumor markers on the surface of the cells. The cells are stained with a light-sensitive dye, placed in a fluid, and passed in a stream before a laser or other type of light. The measurements are based on how the light-sensitive dye reacts to the light.              -   Bone scan : A procedure to check if there are rapidly dividing cells in the bone. A very small amount of radioactive material is injected into a vein and travels through the bloodstream. The radioactive material collects in the bones with cancer and is detected by a scanner.     -   X-ray : An x-ray of the organs and bones inside the body. An x-ray is a type of energy beam that can go through the body and onto film, making a picture of areas inside the body. Sometimes a skeletal survey is done. This is a procedure to x-ray all of the bones in the body.    -   CT scan (CAT scan): A procedure that makes a series of detailed pictures of areas inside the body, taken from different angles. The pictures are made by a computer linked to an x-ray machine. A dye may be injected into a vein or swallowed to help the organs or tissues show up more clearly. This procedure is also called computed tomography, computerized tomography, or computerized axial tomography.    -   MRI (magnetic resonance imaging): A procedure that uses a magnet, radio waves, and a computer to make a series of detailed pictures of areas inside the body. A substance called gadolinium may be injected into a vein. The gadolinium collects around the LCH cells so that they show up brighter in the picture. This procedure is also called nuclear magnetic resonance imaging (NMRI).    -   PET scan (positron emission tomography scan): A procedure to find tumor cells in the body. A small amount of radioactive glucose (sugar) is injected into a vein. The PET scanner rotates around the body and makes a picture of where glucose is being used in the body. Tumor cells show up brighter in the picture because they are more active and take up more glucose than normal cells do.    -   Ultrasound exam: A procedure in which high-energy sound waves (ultrasound) are bounced off internal tissues or organs and make echoes. The echoes form a picture of body tissues called a sonogram. The picture can be printed to be looked at later.    -   Bronchoscopy : A procedure to look inside the trachea and large airways in the lung for abnormal areas. A bronchoscope is inserted through the nose or mouth into the trachea and lungs. A bronchoscope is a thin, tube-like instrument with a light and a lens for viewing. It may also have a tool to remove tissue samples, which are checked under a microscope for signs of cancer.    -   Endoscopy : A procedure to look at organs and tissues inside the body to check for abnormal areas in the gastrointestinal tract or lungs. An endoscope is inserted through an incision (cut) in the skin or opening in the body, such as the mouth. An endoscope is a thin, tube-like instrument with a light and a lens for viewing. It may also have a tool to remove tissue or lymph node samples, which are checked under a microscope for signs of disease.    -   Biopsy : The removal of cells or tissues so they can be viewed under a microscope by a pathologist to check for LCH cells. To diagnose LCH, a biopsy of bone lesions, skin, lymph nodes, or the liver may be done.