Most common primary malignant bone tumour?

Most of us may get confused about the most common primary malignant bone tumour. Some say it is multiple myeloma while some other may think it is osteosarcoma. Lets delve into the details. 

A famous question for the MD/MS/PG entrance questions is asking about the most common primary malignant tumour of the bone. Options include multiple myeloma, osteosarcoma, osteoclastoma, Ewing’s sarcoma. Aspirants get confused betwwen multiple myeloma and osteosarcoma. Even I had got confused for a long time and I finaly got to know the answer 

Multiple myeloma is the most common primary malignant tumour of the bone. It is also known as Kahler’s disease. However, since it arises from the antibody producing plasma cells within the bone marrow, it is not considered a true primary bone tumour. Just don’t get confused between primary and true means the same. 

A expository image showing the anatomy of bone
picture courtesy of  american cancer society

Another clue to solving the MCQs about bone tumour 

Osteosarcoma is the most common true primary malignant tumour of the bone. Chondrosarcoma is the second most true primary malignant tumour of the bone 

multiple myeloma is the most common primary malignant tumour of the bone

So, what is the most common bone tumour ?

Undoubtedly, metastases are the most common bone tumour. Though they are secondary tumours, they form the most numerous incidences among bone tumours. 

Other important facts you must know about bone tumours

Multiple Myeloma is associated with CRAB findings. CRAB = Hypercalcemia, Renal failure, Anaemia and Lytic Bone lesions. It arises from the bone marrow inside the  Most common immunoglobulin to raise in multiple myeloma is IgG followed by IgA whereas must common immunoglobulin to rise in MGUS (monoclonal gammopathy of undetermined significance) is IgM. 

Osteosarcoma is bimodal in distribution, along with Hodgkin’s Lymphoma. It is the second most common primary malignancy of the bone. It can be caused by Paget’s disease of the bone. Osteosarcoma following Paget’s disease most commonly arises in the pelvis.

Osteochondroma is the most common benign tumour of the bone while osteoid osteoma is the most common true benign tumour of the bone. 

Ewing Sarcoma was first described by Dr. James Ewing in 1921. It is characterised by FLI:EWS traslocation in 11:22. Remember that FLI gene is present in chromosome 11 while EWS is present in chromosome 22. 

Giant cell tumour (osteoclastoma) is found in epiphysis. It is a benign tumour. Chondroblastoma, malignant tumour of the cartilaginous origin is also found is epiphysis

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