Matrix Forming Bone Tumors – Common in young people

1. Bone Forming TMRs

   1. Osteoma

      1. BENIGN bone tumor made of lamellar/woven cortical or trabecular bone in the skull (looks like a lump) and is just an aesthetic problem.

   2. Osteoid Osteoma

      1. Occurs in ages 5-25 in the cortex of long bones (most commonly the tibia and femur); also in the vertebral column.

      2. Clinically

         1. Pt. has a “pain syndrome” characterized by: (1) severe, local pain that is (2) worse at night and (3) relieved by ASA (aspirin).

         2. Occasionally has other symptom complexes.

      3. Radiographically

         1. X-ray shows lesional “nidus” (<>

            1. Nidus consists of vascular TSU/osteoblasts and osteoid in the middle.

         2. CT: shows well circumscribed lesion w/ radio-dense center (mineralized)

      4. Microscopically, you see vascular TSU w/immature small bone spicules w/ # of osteoblasts and osteoclasts.

      5. Tx involves excision of affected segment of cortex.

   3. Osteoblastoma

      1. This is a big osteoid osteoma (> 2cm) more in the spine, less painful (no “pain syndrome”), and less ASA sensitive.

   4. Osteosarcoma

-#1 bone sarcoma (remember this for all the standardized tests you will ever take)

1. Epidemiology

   1. 75% of the cases are in the age range of 5-20 (mostly adolescent males)

   2. have a 2nd peak in the elderly due to diseases causing  bone turnover (Chronic Osteomyelitis, Paget’s Disease)

   3. Molecular Biology

      1. with Hereditary retinoblastoma mutation (Rb) = 100x’s relative risk of getting osteosarcoma

      2. Sporadic osteosarcoma due to p53 mutations but rarely any Rb mutations

2. Site is usually in the metaphysis (area of greatest turnover) with >50% around the knee.

   1. In the proximal femur and distal tibia; sometimes proximal humerus

   2. in older pts. osteosarcoma occurs in the flat and long bones

   3. other site %’s

      1. >50% around the knee

      2. 15% in the pelvis (or proximal femur)

      3. 10% in the shoulder (humerus)

      4. 8% in the jaw

3. Diagnosis

   1.  grade malignancy w/ aggressive changes on X-ray

   2. Malignant cells make osteoid matrix in a “lace-like” pattern. – “odd looking bone formations”

-cells are hyperchromatic, irregular, mitotic activity

3. X-ray of metaphysis of the knees

-show the aggressiveness b/c the bone cannot contain the TMR, often with matrix mineralization.

4. Tx: ChemoTx to kill TMR then surgery to remove it.

5. Prognosis:

   1. METS

      1. 80% of Osteosarcomas will NOT metastasize

      2. Of the remaining 20% that have METS, spread is initially to the lungs and then elsewhere from there. (This is characteristic of sarcomas - vs. carcinoma that has lymphatic spread then goes to the lungs.)

   2. 50-60% 5-Year-Survival w/ aggressive surgery and chemoTx.

6. Other

   1. ex. 17 year old with ’d density of metaphysis (matrix formation is a mixture of bone and periosteum)

7. SLIDES:

   1. x-ray of adolescent male w/ classic osteoma: eccentric TMR w/mixture of periosteal reaction and bone TMR. The periosteum is lifted, forming Codman’s Triangle

   2. Distal femur w/ mineralized bone TMR in the cortex – changes the shape of the soft TSU and the bone.

-because of the spread of the metaphysis, the osteosarcoma can affect higher in the shaft.

3. Histo: lamellar bone w/irregular mineralized matrix (bony trabecule) instead of the marrow being there – called dystrophic calcification. See a lacy matrix

4. Histo: Pink mesh of osteoid = osteosarcoma

Category: Orthopedics Notes