Bone tumors

Bone tumors form when a bone cell divides uncontrollably and forms a mass or tumor.

If the tumor remains confined and doesn’t spread into surrounding tissues, then it’s considered benign.

But if the tumor invades into surrounding tissues and metastasizes or spreads through blood or lymph, then it’s considered malignant.

Malignant tumors can either be primary which is when they arise from the bone cells, or secondary, which is when a tumor developed somewhere else in the body, metastasized, and spread to the bones.

The most common sources of tumor cells that affect the bones but start somewhere else in the body, are the breast, prostate, the lungs, the thyroid, and the kidneys.

Now, even though the bones vary in size and shape, they are all made of the same types of cells, and chief among them are osteoblasts which build up new bone, and osteoclasts which help with bone breakdown or resorption.

Now in addition to these, there are some more primitive cells in the bone marrow called human mesenchymal stem cells and neuroectodermal cells, which have the ability to differentiate into many cell types including nerve, fat, bone, and cartilage cells.

Now, in terms of anatomy, looking at a long- bone like the femur - it has two epiphyses, which are the ends that contribute to joints with other bones.

Between the two epiphyses, is the diaphysis, also called the bone shaft.

In children and adolescents, there is an additional narrow portion between the epiphysis and the diaphysis called the metaphysis.

The metaphysis contains the growth plate, the part of the bone that grows during childhood.

In adults the growth plate has ossified and fused with the diaphysis and the epiphysis.

Now, there are genes that promote normal cell growth called proto-oncogenes.

With mutations, proto-oncogenes become oncogenes, and these overstimulate the cell growth.

To balance out cell growth, there are other genes called tumor suppressor genes which promote apoptosis or cell death of mutated cells.