Webster's New World Medical Dictionary

bone cyst, aneurysmal
A benign lesion in a
bone that contains connective tissue and blood
inside a thin bony shell. Aneurysmal bone cysts act
like tumors and expand the bone, and they typically
occur in the second decade of life. They can affect
any bone in the arms, legs, trunk, or skull.
bone cyst, simple
A solitary fluid-filled cavity
(cyst) in a bone, usually in the shaft of a long bone,
especially the humerus, in a child. A simple bone
cyst can cause pain in or near the bone. Also known
as unicameral bone cyst and solitary bone cyst.
bone density
See 
bone mineral density
.
bone marrow
The soft blood-forming tissue that
fills the cavities of bones and contains fat and imma-
ture and mature blood cells, including white blood
cells, red blood cells, and platelets. Diseases or
drugs that affect the bone marrow can affect the
total counts of these cells.
bone marrow aspiration
The removal of a
small amount of liquid bone marrow through a nee-
dle. The needle is placed through the top layer of
bone, and a liquid sample containing bone marrow
cells is obtained through the needle by sucking
(aspirating) it into a syringe. The suction causes
pain for a few moments. Bone marrow aspiration is
done to diagnose and follow the progress of various
conditions, including anemia and cancer, and to
obtain marrow for transplantation.
bone marrow biopsy
The removal of a sample
of bone marrow and a small amount of bone
through a large needle. Two samples are taken. The
first is bone marrow by aspiration (suction with a
syringe). The second is a core biopsy to obtain bone
marrow along with bone fibers. After the needle is
removed, this solid sample is pushed out of the nee-
dle with a wire. Both samples are examined under a
microscope to examine the cells and the architec-
ture of the bone marrow.