Osteogenic sarcoma. Malignant synovioma. Anatomic sites, microscopic & gross pathomorphology.
Primary bone tumors are rare, secondary metastatic bone tumors are more common. Here we’ll take a look at some:
- Benign
- Osteoma - facial bones and skull
- Histologically similar to normal bone, bony protrusion on bones surface
- Osteoid osteoma - metaphysis of femur and tibia
- Histologic pattern of interlacing trabeculae of woven bone. Often arise beneath the periosteum. Appear as a small nidus surrounded by reactive bone.
- Osteoblastoma - vertebrae
- Morphologically and histologically similar to osteoid osteoma
- Malignant
- Primary osteosarcoma - metaphysis of distal femur, proximal tibia and humerus
- Malignant osteoblasts forming osteoid, possibly with cartilage
- Gross appearance shows gritty gray-white tumors, tumor cells are very heteromorphic and hyperchromatic nuclei with giant cells.
- Secondary osteosarcoma - femur, humerus and pelvis
- Histologically the same as primary osteosarcoma
Remember: osteosarcoma is the most common primary malignant bone tumour (after myeloma), peaking in adolescents, often around the knee. On X-ray it is a destructive, mixed lytic and sclerotic mass that lifts the periosteum (Codman triangle). Risk factors: RB1 and TP53 mutations (hereditary retinoblastoma, Li–Fraumeni syndrome); in older adults, Paget disease and previous radiation.
Malignant synovioma
A malignant synovioma (or synovial sarcoma) is form of cancer that occurs in close proximity to the joint capsules, it is a soft tissue sarcoma.
Most commonly occurs near large joints of arm and leg, but can be found in other locations. Histology shows two cell types, a fibrous spindle cell, and an epithelial like cell. Often both cell types appear (biphasic), but some tumours have only spindle cells (monophasic).
Most malignant synovioma are a result of genetic mutation t(X;18).