I am here to go one step further into what was left behind. We will cover another huge but important topic while having a blast. Hope you have liked my previous blog where I have talked about bone structure, fractures and fibrous dysplasia.
This time around, I will focus solely on:
- Primary bone tumor
Yes, that’s all there could be.
Primary bone tumors
As I have mentioned in my previous blog, bone tumor is mostly occurred by metastasis especially 1o bone tumors.
Osteochondroma: ‘Osteo’ related to bone, ‘chond’ related to cartilage and ‘oma’ means benign cancers. Therefore, osteochondroma means tumor of bone and cartilage that occurs at bone’s end near to growth plate(A#1) where a lateral bony projection arises out of the plate.
- Metaphysis of long bones like of leg, pelvis or shoulder blade are commonly affected.
- It most common benign bone tumor that rarely converts into chondrosarcoma(A#2).
- Epidemiology: Males below 25 years of age.
- Causes: Unknown.
- Lateral bony projection (from growth plate) near joints that is painless
- Irritation or pain while exercise
- Numbness in nearby muscles as nerves get compressed
- Could be asymptomatic
- Diagnosis: Common imaging methods like X-ray, CT scan, MRI.
- Treatment: Surgery called excision where tumor is dissected from the bone itself.
A#1. Growth plate: These are the growing regions in teens or young adults.
- These are cartilages at ends of long bones.
- These get hardened with growth where they get widened and lengthier.
- Stops growing at age 20.
A#2. Chondrosarcoma: A malignant cancer of cartilage of arm, thigh, pelvis. Though, I will cover it again later.
- Causes: Unknown but theorised to be generic.
- Symptoms: Swelling because of mass growth, pain, joint stiffness and limited joint movement.
- Treatment: Surgical removal, radiation or chemotherapy.
- Bony mass of less than 2 cm grows with radiolucent unmineralized protein mixture that is secreted by osteoblasts i.e. osteoid.
- Osteoid is weaker than normal bone which makes it prone to fracture.
- Usually affected bones are cortex of long bones like femur or tibia.
- Epidemiology: Occurs more in males that are 25 years of age.
- Causes: Unknown.
- Symptoms: Dull, moderate pain that worsens at night.
- Diagnosis: X-Ray, CT scan, biopsy i.e. tissue is collected from the affected part and observed under a microscope.
- Sometimes, it self-heals. Till that NSAIDs like aspirin and ibuprofen are taken for bone pain.
- Though, if the pain is intolerable for patient, surgical removal could be performed.
- Most common tumor of paranasal sinuses(A#3).
- Benign bone tumor at surface of facial bones or sometimes at neck.
- Associated with Gardner syndrome(A#4).
- Epidemiology: Occurs mainly in middle aged males.
- Causes: Unknown.
- Sinus infections
- Sensory problems like hearing or vision loss
- CT scan
- Routine exam- Where doctor asks some pathological symptoms if the patient is having or not
- Treatment: Treatment is recommended primarily if the tumor is symptomatic.
- Surgery called Expanded Endonasal Approach which is a minimal invasive surgery where an endoscope is inserted via nose upto skull base or near to upper cervical vertebrae. Then tumor is removed without skull opening.
- Percutaneous radiofrequency ablation– Means radio waves which burns the tumor superficially.
A#3. Paranasal sinuses: Regions inside nasal cavity that are filled with air that makes sound resonating and head light. There are 4 types of sinuses according to the bone they are in.
- Frontal- Paired sinuses in frontal bone.
- Sphenoid- Paired sinuses in sphenoid bone’s body.
- Ethmoid- 3 sinuses in ethmoid bone which are anterior, middle and posterior.
- Maxillary- Paired sinuses located below nasal cavity and are largest of all.
A#4. Gardner syndrome: A type of FAP (familial adenomatous polyposis where whole colon has adenomatous polyps i.e. growth of mass cells that can turn cancerous) which is also associated with osseous and soft tissue tumors i.e. osteomas of skull or mandible.
- In this, there are more teeth than the normal number i.e. supernumery teeth.
- It is diagnosed by examining the eye as there is a flat dark spot in retina due to hypertrophy of retinal pigment epithelium.
- Skin is diagnosed with cysts, fibromas. It is a connective tissue growth called fibromatosis.
- A non-malignant slow tumor where healthy bone is dissolved and osteoid is formed around the bone making it weaker and vulnerable to break.
- Commonly occurs in spine i.e. vertebrae.
- Histologically similar to that of osteoid osteoma.
- Though, bony mass size is larger than 2 cm.
- NSAIDS do not work.
- Epidemiology: Again more males are affected like the previous primary bone tumors.
- Causes: Not known.
- Back pain due to compression of nerves.
- Muscle spasm.
- Scoliosis, sideways bending of spine.
- Mild pain in limbs.
- Diagnosis: As that of osteoid osteoma i.e. X-ray, CT scan or biopsy for confirmation.
- Marginal resection of tumor i.e. where 1 cm and 2 cm of surrounding normal soft tissue and bone tissue respectively, are also removed.
- Radio- or chemo-therapy, if the tumor can’t be treated by any other means.
- Curettage i.e. scraping of bone with a curette which activates the bone matrix to regenerate. Though, the hole simply could be filled with a bone graft or Polymethyl methacrylate (PMMA or bone cement).
Giant cell tumor:
- An osteolytic, local, rare but aggressive tumor occurring at epiphysis of long bones.
- Bones could be of arms and legs like bones near to knee region.
- In this, RANKL (here L is ligand) is a protein expressed on neoplastic mononuclear cells i.e. osteoblast cells which binds to RANK, a receptor for RANKL, expressed on multinucleated giant cells that are osteoclasts-like(Q#1).
- Epidemiology: Young adults or adults i.e. after 20 years of age as bone growth is complete. Risk remains until 40 years of age.
- Causes: Could be a complication of paget’s disease, a disease where new bone keeps on replacing the old developed bone making bone weaker and abnormally shaped due to disruption of bone renewal cycle.
- Fracture, as bone gets weaker.
- Bone mass that is visible and painful.
- Fluid collection in joint causing swelling, pain and restricted movement.
- Radionuclide bone scan, a nuclear imaging method where a radioactive substance is injected into bloodstream.
- X-ray where ‘soap bubble‘ (A#5) are seen on film.
Q#1. What does RANKL do by binding with RANK?
A#1. Receptor activator of NF-kappaB a regulatory protein that induces monocyte/macrophage differentiation or activation into osteoclast cells. Therefore, the interaction between RANKL/RANK controls bone modelling/remodelling along with OPG.
OPG or Osteoprotegerin an inhibitor of such process, is a 3rd regulator making a triad of regulatory proteins of bone formation/remodelling. It is produced by osteoblasts. It binds with RANKL on osteoclasts prevents binding of RANK and RANKL, thereby inhibiting osteoclast activation and hence bone resorption.
A#5. Soap bubble appearance: A bubbly appearance occurred due to lytic and expansible nature of tumor. It is porous within and is surrounded by thin cortex.
- A benign tumor of cartilage that grows on or in bone tissue.
- Occurs in medullary cavity of small bones of mainly hands and feet.
- Less commonly occurs in upper arm, thigh, vertebrae and skull bones.
- Epidemiology: Both sex groups are equally affected.
- Cause: Unknown.
- There are 2 subtypes:
- Enchondroma- More common, occurs in hand, after the 3rd decade of life. Symptoms include pain, fracture risk, painless (therefore often asymptomatic) swelling in finger or tendon.
- Periosteal chondroma- Rare, in periosteum (fibrous connective tissue covering of bone), develops earlier than enchondroma. Symptoms include dull pain, swelling of bone or less likely to be asymptomatic.
- Diagnosis: X-ray, MRI, CT scan.
- Treatment: Surgical removal i.e. curettage.
- If fracture has occurred, it is advised to repair and provide time for healing before surgery.
These all above tumors are primary benign bone tumors. Now we will speak about primary malignant bone tumor which is more common.
Osteogenic sarcoma: or simply osteosarcoma.
- Accounts for 1/5 of all primary bone cancers.
- Aggressive malignant tumor that affects metaphysis of long bones (many times the knee part).
- Osteoblasts produce osteoid.
- Called anaplastic or pleomorphic i.e. cells without specialised characteristics or weakly differentiated.
- Characterised by codman triangle.
- This triangle is observed when periosteal reaction of a bone lesion grows so destructively that it tears of the periosteum and does not allow it to newly lay down. This newly formed periosteum gets lifted off either at the end of lesion or in the centre of lesion without any remarkable ossification. This gives, while looking at the radiological film, a triangular visual.
- Primary tumor is seen in males before their bone growth stops.
- Secondary tumor is usually seen in older people especially who have any bone infarct (tissue necrosis due to inadequate blood availability), paget’s disease, Li-Fraumeni syndrome (A#6) and eye cancer or simply familial retinoblastoma.
- Cause: Gene mutations that could be either familial/inherited or acquired in person’s life.
- Symptoms: Swelling, pain (knee pain).
- Diagnosis: Sunburst pattern (A#7) is seen in X-ray. Also MRI or CT scan can be performed.
- Primary tumor can be treated with radiation-chemotherapy, surgery like bone grafting.
- Secondary tumor has poor prognosis that to remove by surgery even limb amputation could have to be done.
A#6. Li-Fraumeni syndrome: A very ugly disease with multiple malignancies at young age. It is commonly called SBLA cancer syndrome as the tumors are Sarcoma, Breast, Leukemia and Adrenal gland.
A#7. Sunburst pattern: Lesion grows faster than periosteum could be laid down where Sharpey’s fibers spread transversely to the bone.
Sharpey’s fibers are type I collagen fiber bundles in connective tissue matrix that connects periosteum to the bone.
- Primary malignant tumor just like osteosarcoma but here, it is in diaphysis of femur or flat bones of pelvic.
- Characterised by small blue cells ,derived from neuroectoderm, during histology.
- Epidemiology: Common in young boys of age below 15 years.
- Cause: It is identified by reciprocal (gene exchange of non-homologous chromosomes) translocation t(11;22) where genes EWing Sarcoma (chromosome 22) and Friend Leukemia virus Integraion (chromosome 11) are fused to translate protein EWS-FLI1.
- EWS-FLI1 protein is an abnormal transcription factor governs many genes expression and oncogenic processes leading to formation of ewing tumor.
- Symptoms: Pain and swelling on tumor area i.e. bones, joints.
- Occasionally, tumor could grow in spine causing suppressing of nerves causing paralysis.
- Occasionally, fracture.
- Diagnosis: X-ray, MRI or CT scan.
- During radiography, a unique feature i.e. ‘onion skin’ can be seen.
- It appears due to periosteal reaction that layers over stretched lesion.
- Treatment: Chemotherapy or amputation.
- A malignant bone cancer in chondrocytes.
- After osteosarcoma, it is the 2nd most common primary bone cancer.
- It is a tumor of medulla (medullary cavity) of femur (proximal i.e. part near to the body centre), humerus and bones located in pelvis.
- Epidemiology: Risks of developing increases with age.
- No differentiation between the sexes.
- Causes: Unknown.
- Symptoms: Growth and swelling on bone.
- Pain increases with time and worsens at night.
- Diagnosis: Biopsy, X-ray, CT scan.
- Treatment: Radio-chemotherapy, surgery.
So, this was all from me for you about primary bone tumors. I hope you have liked it, let me know. If not, well, let me know again.
The next blog is again going to be about bone related. In the next blog I will be covering… why not let be suspense! Whatever it will be, I am sure you will be glad to know something new.