Biopsy
The diagnosis of NHL requires a biopsy of an involved lymph node or another involved organ (bone, lung, liver or skin). This helps the doctor determine if the cancer is non-Hodgkin's and, if so, which subtype.

The physician may order a fine-needle aspiration (FNA) biopsy, which uses a syringe with a thin needle to withdraw a bit of tissue from a tumor. A computed tomography (CT) scan may be used to help the doctor guide the needle if the growth is deep inside the body. In CT imaging, a scanner moves around the body taking hundreds of X-ray images, which a computer then combines to make a three-dimensional image of the inside of the body.

The doctor may cut through the skin to remove a whole lymph node or may remove part of a tumor. If the cancer is near the surface of the skin, the child will require only local anesthesia. If it is deep inside the body, general anesthesia will be used.

To see how far the cancer has spread, a bone marrow aspiration and biopsy may be performed. This test helps doctors see whether any cancer cells have invaded the bone marrow. Bone marrow is usually removed from the back hip bone by a procedure called aspiration suctioning a small amount of marrow through a hollow needles) or by biopsy, which involves taking a small piece of bone and marrow with a longer hollow needle.

The physician may also do a lumbar puncture or spinal tap. This involves inserting a needle between two of the lower back bones (vertebrae) to withdraw a small amount of spinal fluid to examine under a microscope for cancer cells. This test shows whether cancer cells are in the spinal fluid, which bathes the brain and spinal cord.

Imaging
The doctor may perform a variety of imaging tests to detect enlarged lymph nodes or tumors and to see where the cancer is located and if it has spread.

The doctor may order a chest or abdominal X-ray to detect tumors in these areas. An abdominal ultrasound, which uses sound waves to create images, may also be performed. The physician may order a CT scan. Sometimes a special dye is injected to help provide better detail. An ultrasound, which uses sound waves to create images of the body, or a magnetic resonance imaging (MRI) scan, which uses electromagnetic waves to create pictures of internal organs and tissues, are other options.