Bone marrow biopsy

Most people with suspected systemic mastocytosis receive a bone marrow biopsy as part of their diagnostic testing.  Sometimes people will have confirmed mast cell infiltration in another organ, in which case a bone marrow biopsy may not be needed. 

I know that once I needed a bone marrow biopsy, I sort of felt like my illness had hit the big time.  Like it was time to be really concerned.  My family and friends were really concerned because bone marrow biopsies are used to diagnosis serious diseases.  It is okay to be scared.  But the procedure was not even close to the worst I’ve had, and the pain was manageable. 

In the middle of long bones, there is a squishy center called bone marrow.  Your bone marrow produces most of your body’s blood cells.  The marrow is essentially organized tissue that holds the immature blood cells.

Red bone marrow is active and produces red blood cells, platelets, neutrophils, basophils, eosinophils, monocytes/macrophages, T cells, B cells and mast cells.  Yellow bone marrow mostly contains fat.  Red bone marrow is found in flat bones, like the sternum (breast bone) and the pelvic girdle (upper hip bones.)  In children, the femur (thigh bone) also contains red marrow.

A bone marrow biopsy removes some of the solid tissue from the red marrow to look for abnormal cells.  It uses a long, hollow needle.   Using this needle, a solid piece of bone marrow is removed.  This is called a core. 

A bone marrow aspiration, which removes some liquid from the red marrow, is often done at the same time.  It uses a syringe to remove a little bit of the liquid. 

When you arrive, you may be given IV sedation.  You usually have to request this in advance.  Generally, this is “twilight sedation,” in which you are awake but given medications to relax and manage the pain. 

If they are taking samples from the back of your pelvic crest, you lay on your stomach.  You receive a local anesthetic, typically lidocaine.  It will burn as the drug numbs the area.  (I’ve always found it really ironic that an anesthetic burns.)  A small incision is made in the skin at the biopsy site. 

A hollow needle is then pushed through the bone and into the marrow.  A syringe is attached to the needle and the person doing the procedure pulls back on the plunger to draw liquid into the needle.  This is called the aspirate.  When the aspirate is removed, it changes the pressure inside the bone and causes some pain.  Sometimes no aspirate is found.  This is called a “dry tap.”  If this occurs, another site is biopsied. 

After the aspiration, the biopsy is performed.  This uses a larger hollow needle that is pushed through the bone and into the solid marrow.  The entire procedure (aspiration and biopsy) usually takes about 30 minutes.

After the samples are taken, a sterile dressing is applied to the site with pressure to stop bleeding.  Once the bleeding has stopped, a new dressing is taped into place.  It is important to keep this dressing dry for 24 hours, as getting it wet can increase the risk of infection.  After 24 hours, you can shower or swim as usual. 

The biopsy site will be sore for at least a few days.  Avoid strenuous activity for a few days.  If you develop an (unusual) fever, severe pain, swelling, redness or drainage from the site, or uncontrolled bleeding, contact your health care provider.  This can indicate an infection.

People ask a lot if the biopsy hurts.  With twilight sedation, it hurt, but not badly, and not for long.  I was pretty sore for about a week after, with a throbbing pain that went down my right leg.  I didn’t have any problems otherwise.    

For people with mast cell disease, there are additional steps and precautions that need to be taken.  When I had mine, I premedicated 12 hours before the procedure, and was then given IV medications an hour before the procedure.  12 hours before, I took 50 mg prednisone, 150 mg ranitidine, 10 mg montelukast and 50 mg diphenhydramine.  One hour before, I received 120 mg methylprednisolone, 40 mg famotidine, and 50 mg diphenhydramine. 

Care must be taken with pain medication for people with mast cell disease.  I received midazolam and fentanyl.  I was advised by my mast cell specialist that I needed to receive twilight sedation for this procedure, as pain is a mast cell trigger, and could cause anaphylaxis for me. 

As always, make sure the medical team is aware of your disease and the procedure if you react/anaphylax/shock.  Always have your Epipens with you.  Never assume that they will have epinephrine in the room.

It is not unusual for multiple biopsies to be needed for diagnosis with SM.  The reason for this is that where the mast cells will cluster in the bone marrow is unpredictable.  Unless you put the needle in the right place, it will be negative.  If you meet three of the minor criteria for SM, you do not need a positive bone marrow biopsy for diagnosis; however, a positive bone marrow biopsy is the most common method of diagnosis.

After the samples are taken, they will be tested for several things.  The samples will be inspected under a microscope to see what types of cells are present and in what quantity, including how many mast cells are present.  There should be some mast cells present, but too many is problematic.  They will also see if they shaped normally, or if they are “spindle shaped,” in which they have pointy edges coming off them (like a star.)  They will use special stains in order to see different cell types, including Giemsa stain for mast cells.

Mast cells in the samples will also be tested for some receptors on their surface, CD117 (encoded by the CKIT gene), CD2 and CD25.  This is done by using special antibodies to these receptors that stick to the receptors, and can then be detected by the operator.  They will also be tested for the D816V mutation in the CKIT gene.  This is done by a testing method called PCR. 

The whole process is not super pleasant, but this test provides answers that are impossible to get otherwise.  And I think you’ll all agree with me that having answers is better than not knowing.