What is the difference between primary and secondary bone cancer?

Distinguishing between primary and secondary bone cancer is crucial for understanding the nature of the disease and determining the appropriate course of treatment. Primary bone cancer originates directly from the cells of bone tissue, while secondary cancer occurs when cancer cells from another part of the body spread to the bones.

Primary Bone Cancer: Origin and Types

Primary bone cancer is a rare type of cancer that originates in the bones themselves. This type accounts for less than 1% of all newly diagnosed cancer cases [1]. Primary bone tumors can be benign (non-cancerous) or malignant (cancerous). Although both types may grow and press on healthy bone tissue, benign tumors usually do not spread or destroy bone tissue and are rarely life-threatening [1].

Types of primary bone cancer are classified based on the type of cells from which the tumor originates [1]:

• Osteosarcoma: Originates from bone-forming cells (osteoblasts). It often occurs in the arm near the shoulder and in the leg near the knee in children, adolescents, and young adults, but it can occur in any bone, especially in the elderly. This tumor grows quickly and often spreads to other parts of the body, including the lungs [1].
• Chondrosarcoma: Starts in cartilage tissue. It most often forms in the pelvis, the upper leg, and the shoulder. It typically grows slowly, although it may sometimes grow quickly and spread. It occurs mainly in older adults (over 40 years old) [1].
• Ewing Sarcoma: Usually arises in bones, but it can also arise in soft tissues. It often forms in the pelvis, legs, or ribs, but it can form in any bone. This tumor grows quickly and often spreads to other parts of the body, including the lungs [1].
• Chordoma: A very rare tumor that forms in the bones of the spine, usually occurring in older adults at the base of the spine (sacrum) and the base of the skull [1]. In children and adolescents, it often forms at the base of the skull [3].

Secondary Bone Cancer (Bone Metastases): Spread and Impact

Cancer that spreads to the bones from other parts of the body is called metastatic (or secondary) bone cancer. It is referred to by the original name of the organ or tissue where it started, for example, breast cancer that has spread to the bones [1]. In adults, cancer tumors that have spread to the bones are much more common than primary bone cancer [1].

Although most types of cancer can spread to the bones, bone metastases are particularly likely with certain types of cancer, including breast and prostate cancer [1].

Common and Different Symptoms

Pain is the most common symptom of bone cancer, but not all bone cancers cause pain. Persistent or unusual pain or swelling in or near a bone can be caused by cancer or other conditions [1]. Other symptoms of bone cancer include a lump (which may be soft and warm) in the arms, legs, chest, or pelvis; unexplained fever; and a broken bone without a known cause [1].

For secondary cancer, metastatic bone tumors can cause fractures, pain, and abnormally high levels of calcium in the blood, a condition called hypercalcemia [1].

Importance of Early Diagnosis

Because some symptoms are similar to other conditions, it is essential to see a doctor to determine the cause of any bone-related symptoms [1]. Diagnosis usually includes a medical history and physical examination, as well as imaging tests such as X-rays, bone scans, computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) scans [1]. A final diagnosis often requires a biopsy (a tissue sample from the tumor) to determine if cancer is present [1].

Next Steps and Medical Care

If you are experiencing persistent pain or swelling in the bones, or any of the symptoms mentioned above, it is important to consult a doctor immediately. A doctor can evaluate the symptoms and perform the necessary tests to determine the cause. Early diagnosis allows for broader treatment options and improves potential outcomes. For more information on bone cancer types, symptoms, and early diagnosis, you can visit Bone Cancer: Types, Symptoms, and Early Diagnosis (Arabic).

Medical references

• Primary Bone Cancer
• Childhood Chordoma (PDQ®)–Patient Version