<B>Metastatic tumor in bone </B>

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Metastatic tumor in bone

Etiology:

• The metastases arise as part of the natural history of malignancies in various organs.

Pathogenesis:

• Spread may occur through direct extension (from viscera in close proximity to bones); by vascular or lymphatic dissemination; or by direct seeding.
• The resorption of bone seen in the vicinity of tumor metastases is believed to be due to activation of osteoclasts by cytokines aberrantly secreted by tumor cells.
• Similarly, excess mineralization seen in some cases of tumor deposits in bone is also due to inappropriate cytokine release from the tumor cells.

Epidemiology:

• Malignancies of various organs and tissue commonly metastasize to bone.
• Malignancies of breast, prostate, lung, kidney and thyroid are frequent sources of metastatic deposits in bone.

General Gross Description:

• Grossly, lesions replace bone and appear as soft tissue masses of varying sizes.
• Hemmorhage and necrosis are frequently seen.
• Lesions can contain gritty areas due to reparative bone deposition within the tumor.

General Microscopic Description:

• The tumor deposits resemble the primary tumor.
• In some instances, the metastasis may be more or less well differentiated than the primary focus.
• There is often evidence of osteoclastic activity and bone resorption in the vicinity of the tumor. Some tumors (such as adenocarcinoma of the prostate) may cause bone deposition due to activation of osteoblasts.

Clinical Correlations:

• Metastases in bone manifest themselves by a pathological fracture or severe intractable bone pain.
• Pathological fractures are fractures of bones which occur as a result of stress normally insufficient to break a bone.

References:
•Robbins "Pathologic Basis of Disease". (Cotran, Kumar and Robbins, Eds.) 5th Edition. pp 1246.