Yes, in all likelihood, you will be asked to undergo a bone marrow biopsy at some point in your diagnosis or treatment. In some major cancer centres, bone marrow biopsies are not performed until treatment begins.

There are two procedures used for obtaining bone marrow samples: the bone marrow aspirate which is used to obtain a small amount of marrow from inside the bone, and the bone marrow biopsy which is used to obtain a sample from the bone showing the structure of the bone marrow cavity.

Aspiration works extremely well when there is little or no fibrosis (when the cells in the marrow are not tightly packed) and when some cells are individual (not so tightly bound to each other that they look like a single entity). This is because of the need to force single cells to come into the syringe by applying a vacuum. Biopsies work well when there are decreased numbers of cells or the cells form tight packets. Many facilities perform both in the same procedure. The aspirate is done first and then the "core" biopsy is performed. This provides the best of both worlds with only one needle insertion.

These procedures are useful in confirming CLL, determining the extent of the disease, and deciding on treatment. The pattern of lymphoid infiltration in the biopsy specimen of the marrow also provides useful prognostic information--diffuse involvement correlates with progressive or advanced disease, while nodular or interstitial (non-diffuse) patterns predict a better prognosis.

The samples are usually obtained from the back of the hip bone, although the breast bone (sternum) may be used instead for bone marrow aspirates only. These procedures cause some brief and usually mild discomfort. They are usually carried out with local anaesthetic, although oral or intravenous sedation may also be available.