Collection of Hematopoietic Stem Cells

What is hematopoietic stem cell collection?

Stem cell collection, also known as hematopoietic progenitor cell harvest, is a form of an apheresis procedure known as leukapheresis. It is used to treat certain types of cancer and autoimmune diseases.

Stem cells are immature cells from which the different types of blood cells can grow. Stem cells are produced in the bone marrow, which is inside the bones. Small numbers of stem cells circulate in the blood stream, called peripheral blood stem cells.

The best time to collect peripheral blood stem cells is when the stem cells are at their highest levels in the blood. This is usually four to five days after your child receives specific medications — called growth factors — that stimulate cells to grow. These medications are prescribed by your child’s transplant physician at Children’s Hospital of Philadelphia.

Who needs hematopoietic stem cell collection?

If your child has neuroblastoma, a brain tumor, lymphoma or leukemia, your child’s doctor may recommend stem cell collection as part of your child's treatment.

Occasionally, peripheral blood stem cell collection is recommended for a child with certain genetic diseases that lead to autoimmune deficiency and anemia.

Stem cell collection can be performed on babies, children and adults.

What to expect

If your child is referred to the Apheresis Program for stem cell collection, they will have an initial evaluation by a physician-nurse team in the Apheresis Unit. The apheresis team will already know about your child's condition from your child’s treating physician.

Prior to the apheresis collection procedure, your child’s transplant staff and experts from the Apheresis Program will check to see if your child has adequate veins for the large needle generally used in stem cell collection.

Many young children have thin, fragile, and/or small veins that are difficult to access. In that case, your child will need a central venous catheter (CVC) or port placed in CHOP’s Intervention Radiology Unit or operating room. Your child will be sedated and will not have any pain during catheter/port placement.

On the day of your child’s procedure, our team will greet you and your child when you arrive. You will be directed to a patient area that includes:

  • A reclining chair or bed for your child
  • A high-tech apheresis machine that will be customized for your child’s size and procedure
  • Room for you to sit with your child
  • A television to distract and entertain your child

Your child’s procedure will be overseen by board-certified apheresis physicians, experienced apheresis nurses and child life staff. One or more team members will be with your child at all times to provide comfort, answer questions, and ensure the procedure goes smoothly.

How is stem cell collection performed?

For stem cell collection, your child’s blood will be withdrawn through a needle or catheter into a cell separator machine that separates the blood using a centrifuge. White blood cells containing stem cells are collected in a bag, while the rest of your child’s blood is returned through another vein or catheter. This procedure is called apheresis.

If your child has adequate veins for a large needle, an apheresis nurse will insert needles into the veins of both of your child’s arms to withdraw and return the blood. If your child has a central venous catheter (CVC) or port, blood will be withdrawn from one side, and returned to the other side.

Children who are especially small (weighing less than 25 Kg), or have anemia (low red blood cell count) will receive a blood transfusion with packed red blood cells (called blood prime) at the beginning of their stem cell collection procedure.

In addition, all children will receive a small amount of blood thinning medications called anticoagulants — either citrate or heparin — to prevent their blood from clotting during the procedure. The apheresis physician will determine which anticoagulant, or a combination of the two, your child will receive based on your child's condition and lab tests.

The cycle of drawing and returning your child’s blood is done simultaneously, so your child’s circulating volume remains stable.

Stem cell collection may take three to five hours to complete, depending on how many peripheral blood stem cells are required. In some cases, your child may need to return in the next day or two for additional stem cell collection. In most cases, after collection is complete, children can return to school or other activities within one day.


Stem cell collection is a safe procedure, but side effects can occur. Your child may experience:

  • Symptoms similar to regular blood donation, such as nausea, vomiting, dizziness or fainting
  • Problems related to the anticoagulant, including sour taste in the mouth, tingling around the lips, muscle cramping, irregular heartbeat, or prolonged bleeding
  • Bruising, numbness, pain or infection at the site of the needle stick or catheter insertion
  • Low or fluctuating blood pressure
  • Reactions related to a blood transfusion (if needed), including itching, rash, hives, shortness of breath, back pain or fever

If your child experiences any of these symptoms, please tell your child’s medical team.


If your child is having stem cell collection before other treatment — such as chemotherapy, radiation or organ transplant — the stem cells may be frozen and stored. After treatment, the stem cells may be reinfused into your child's body. The stem cells will boost your child’s immune system and help regrow body cells.

There are no direct benefits for stem cell donors who are not reinfused with their own cells.