Trephine Biopsy: Definition
A trephine biopsy removes a small, solid core of bone and bone marrow. A pathologist then examines it under the microscope. Doctors also call it a bone marrow core biopsy. Doctors usually do it along with a bone marrow aspirate.
This article explains what a trephine biopsy is, why doctors order it, how the laboratory handles it, and what your report may say.
What is a trephine biopsy?
A trephine biopsy takes a narrow cylinder of bone and marrow from inside a bone. Bone marrow is the soft tissue inside bones where the body makes most blood cells. The core is typically 1 to 2 centimeters long. The word trephine refers to the hollow needle that cuts the core.
The core keeps the marrow intact. This lets the pathologist see the pattern the cells form, not just what each cell looks like. A trephine biopsy is one part of a bone marrow biopsy.
How is a trephine biopsy different from a bone marrow aspirate?
Doctors usually take both samples during the same procedure. They give different but complementary information:
- Aspirate. A bone marrow aspirate draws out liquid marrow with a needle and suction. It shows the size, shape, and maturity of individual cells. It does not show the pattern the cells form.
- Trephine biopsy. The core shows marrow structure. It shows how much of the marrow consists of blood-forming cells and how much is fat. It also shows scarring and clusters of abnormal cells.
The core is especially useful when scarring makes it hard to draw out liquid marrow. In that case, the core may be the only sample the pathologist can examine.
Why do doctors order a trephine biopsy?
Doctors order a trephine biopsy to find out why the marrow is not working normally. Common reasons include:
- Unexplained blood counts. Blood tests show too many or too few blood cells.
- Suspected blood cancer. Examples include leukemia, lymphoma, multiple myeloma, and myelodysplastic syndrome.
- Marrow scarring. Conditions such as primary myelofibrosis replace marrow with scar tissue.
- Spread of cancer. Some cancers spread to the bone marrow. Doctors call this metastasis.
- Checking treatment. A repeat biopsy shows how the marrow has responded to treatment.
How do doctors perform a trephine biopsy?
The doctor usually takes the sample from the back of the hip bone, called the posterior iliac crest. The doctor numbs the skin and bone surface with a local anesthetic. The doctor then inserts a hollow needle into the bone and removes a small core sample. The procedure usually takes only a few minutes. You may feel pressure or brief discomfort. Most people go home the same day.
What happens to the sample in the laboratory?
The laboratory first softens the bone so it can be cut into thin slices. Laboratories call this step decalcification. As a result, trephine results usually take one to two days longer than aspirate results. The laboratory then stains the slices so the pathologist can examine them.
The pathologist may order extra stains on the core. These include:
- Reticulin stain. This special stain shows the fine fibers that support the marrow. It helps the pathologist grade fibrosis.
- Iron stain. This stain shows how much iron the marrow stores.
- Immunohistochemistry. Immunohistochemistry uses antibodies to identify specific cell types, such as lymphoma cells or plasma cells.
Other tests, such as flow cytometry and a karyotype, usually use cells from the aspirate.
What might my report say about a trephine biopsy?Trephine findings usually appear alongside the aspirate findings. The bone marrow biopsy report guide explains each section in detail. Common terms include:
- Adequacy. The core contains enough marrow to examine. The report may describe a short core, or one with little marrow, as limited or inadequate.
- Cellularity. The share of the marrow made of blood-forming cells, given as a percentage. Normal cellularity falls with age. As a rough guide, it is about 100 minus your age.
- Normocellular, hypercellular, or hypocellular. The marrow has a normal, increased, or decreased number of blood-forming cells for your age.
- Trilineage hematopoiesis. All three main blood cell lines are present: red cells, white cells, and platelet-producing cells.
- Fibrosis grade. The amount of scarring, from MF-0 (normal) to MF-3 (dense scarring throughout).
- Involvement by a disease. The core contains abnormal cells, such as lymphoma, myeloma, or cancer from another site. The report may give the percentage of marrow involved.
Questions to ask your doctor
- Why did I need a trephine biopsy?
- Was the core large enough to examine?
- What was the cellularity of my marrow, and is it normal for my age?
- Were all three blood cell lines present and normal?
- Did the biopsy show any fibrosis?
- Did the biopsy show any abnormal or cancerous cells?
- Are any special tests still pending?
- How will these results affect my treatment or follow-up?