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High power view of an area of myelofibrosis
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High power view of an area of myelofibrosis

A medium high power view of myelofibrosis.
To the left is a spicule of normal bone.
To the right top of this image (highlighted by the black arrows) is a small fragment of new bone formation.
The recent origin of this bone is indicated by the large number of osteocytes relative to the matrix.
Notice that in the more mature bone to the left, far fewer osteocytes are visible in the lacunae.
The rest of the image is composed of immature fibrous connective tissue instead of the normal marrow elements.
The immaturity of this collagen is indicated by the relatively cellular appearance.
It would be useful to contrast this with mature collagen, best seen in the image entitled "Dermal fibroblasts."
(Description By:T.V.Rajan, M.D. )
(Image Contrib. by:T.V.Rajan, M.D. UCHC )
Myelofibrosis
Etiology

Unknown.
Pathogenesis

The mechanism of myelofibrosis is unknown, but is believed to be due to the abnormal proliferation of fibroblasts in response to cytokines (primarily TGF-beta and PDGF) from megakaryocytes.,
Epidemiology

The disease usually affects individuals late in life (sixth through eighth decade).
Both sexes are equally affected.
General Gross Description

The bone reveals a firm, homogeneous, tan to white appearance instead of the normal appearance of red marrow, flecked with bone spicules.
General Microscopic Description

Microscopically, the entire marrow space is replaced with mature collagen and fibroblasts.
Megakaryocytes may be seen even in late stages.
Clinical Correlation

Clinically, the loss of marrow function in the bone stimulates myelopoiesis in extramedullary sites, such as spleen and liver.
For this reason, the disease is also known as agnogenic myeloid metaplasia.
Symptoms may be due to the enlargement of the spleen (a dragging sensation in the left side); or due to the reduction in red and white cell function.
Sometimes preceded by myelogenous leukemia, or polycythemia vera; often, however, the cause is unknown.
The prognosis is not good, with relatively few individuals surviving five years.
References

Cotran RS, Kumar V, Robbins SL: Robbins Pathologic Basis of Disease. 5th edition. Philadelphia, W.B. Saunders, 1994, pp.660.
Myelofibrosis
Synopsis by: T.V. Rajan M.D. PhD. (T10510M49000)[78]
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