osteoma and osteosarcoma

6. OSTEOID OSTEOMA

11. SYMPTOMS AND IMAGING

12. • Gross Description:
• Oval red nidus is easily
distinguishable from
surrounding tissue
• Soft and friable to sclerotic
nidus
• Surrounded by densely
sclerotic reactive bone

15. Microscopic Description
Nidus:
• Haphazard trabeculae of woven bone with prominent osteoblastic
rimming
• Different thickness and mineralization level
Surrounding bone:
• Thickened trabeculae of bone with adjacent loose fibrovascular
stroma

16. Osteoblastic
rimming
Woven bone
Fibrovascular
stroma

17. OSTEOSARCOMA

18. General Information
• Osteosarcoma is a malignant tumor in
which the cancerous cells produce osteoid
matrix or mineralized bone.
• It is the most common primary malignant
tumor of bone, exclusive of myeloma and
lymphoma
• Accounts for approximately 20% of
primary bone cancers
• Occurs in all age groups

21. • Any bone can be involved.
• The tumors usually arise in the metaphyseal region
of the long bones of the extremities, and
• Almost 50% occur about the knee (i.e., distal femur or
proximal tibia)
• Osteosarcomas typically present as painful,
progressively enlarging masses.
• Sometimes a sudden fracture of the bone is
the first symptom.

25. • Radiographs usually show a large
destructive, mixed lytic and blastic mass
with infiltrative margins ( Fig ).
• Fig : Distal femoral osteosarcoma with
prominent bone formation extending
into the soft tissues. The periosteum,
which has been lifted, has laid down a
proximal triangular shell of reactive
bone known as a Codman triangle
(arrow).

26. Pathogenesis

28. • It is also noteworthy that osteosarcomas peak in incidence around
the time of the adolescent growth spurt and occur most frequently in
the region of the growth plate in bones with the fastest growth.
• The increased proliferation at these sites may predispose to
mutations that drive osteosarcoma development.

29. Macroscopically
Osteosarcomas are bulky tumors that are
gritty and gray-white
Often contain areas of hemorrhage and
cystic degeneration (Fig ).
The tumors frequently destroy the
surrounding cortices and produce soft
tissue masses.

30. They spread extensively in the medullary canal, infiltrating and
replacing hematopoietic marrow.
 Infrequently, they penetrate the epiphyseal plate or enter the
joint.

32. Microscopically
• The tumor cells vary in size and shape and
frequently have large hyperchromatic nuclei.
• Bizarre tumor giant cells are common, as
are mitoses, some of them abnormal (e.g.
tripolar).
• Vascular invasion is usually conspicuous, and
some tumors also exhibit extensive necrosis.

33. The neoplastic bone usually has a fine, lace-like
architecture but also may be deposited in broad sheets
or as primitive trabeculae.
The formation of bone by the tumor cells is diagnostic (Fig. )

34. • Fine, lacelike pattern of
neoplastic bone produced by
anaplastic malignant tumor
cells in an osteosarcoma.
• Note the abnormal mitotic
figures (arrow).