Bone Flashcards

1
Q

Features of Osteoma

A
  • Loc: Craniofacial bones, can protrude to sinuses/orbit
  • Rx: Radiodense mass
  • Micro:
    Dense, mature lamellar bone.
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2
Q

Features of Osteoid osteoma

A
  • Clinical: 10-30 yo. Pain relieved by NSAIDS
  • Loc: Any bone. Common: long bones, H&F, vertebra
  • Rx: Radiolucent central nidus +/- radiodense center & peripheral sclerotic reaction
  • Micro:
    Nidus has anastomosing trabeculae of woven bone/osteoid lined by osteoblasts (variably calcified).
    Fibrovascular stroma in b/w trabeculae +/- MN giant cells.
    Nidus surrounded by dense bone.
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3
Q

Features of Osteoblastoma

A
  • Clinical: 5-30 years old. Progressive pain
  • Loc: Post elements of vertebrae, long bones
  • Rx: Radiolucent, well defined, >2cm +/- calcium foci
  • Micro: (like an ostoid osteoma but bigger)
    Anastomosing trabeculae of woven bone/osteoid lined by osteoblasts (variably calcified).
    Ectatic vessels in the fibrovascular stroma +/- MN giant cells.
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4
Q

Features of Osteosarcoma

A

-Clinical: Progressive pain.
10-25yo.
Second peak: >40 years old, associated with pre-exiting disorder: Paget, Radiation, Chemothx, foreign body (i.e at site of THJR, etc), pre-existing benign bone lesion (fibrous dysplasia, OI, bone infarct) and genetic predisposition (hereditary RB, Li-Fraumeni sdme).
-Location:
Metaphysis of long bones (> common around knee).
- Rx: Destruction of medullary cavity & cortical bone, aggressive pattern of periosteal reaction.
- Micro:
* Production of bone or osteoid by the tumour cells: ‘lace-like’ deposition of osteoid +/- calcified matrix.
* No osteoblastic rimming
*Spindled, oval or round cells with cytologic features of malignancy.
* Osteoblastic, chondroblastic & fibroblastic patterns usually coexist.
* Permeative growth.
* +/- HPC like vessels.
* +/- MN gant cells.
- IHC: SATB2 useful to establish osteoblastic lineage.

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5
Q

Bone conditions that predispose to malignancy (4)

A
  • Paget disease
  • Enchondromatosis
  • Osteochondromatosis
  • Fibrous dysplasia
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6
Q

Differential diagnosis of bone lesions with giant cells (9)

A
  • GCT
  • ABC
  • LCH
  • Giant cell rich osteosarcoma
  • Giant cell reparative granuloma
  • Non-ossifying fibroma
  • Chondromyxoid fibroma
  • Chondroblastoma
  • Brown tumour of hyperparathyroidism
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7
Q

Features of Chondrosarcoma (page 1764-1767 Rosai)

A
  • Clinical: Adults >50 years old. Slow clinical evolution with pain, swelling +/- pathological #. Can metastasize to lung.
  • Location:
    Central: Medulla of long or flat bones.
    Peripheral: From the cartilaginous cap of an Osteochondroma (> freq in MHE patients).
    Most common: trunk (including shoulder and pelvic girdles), upper end of humerus & femur, skull.
  • Rx: Large radiolucent lesion with areas of calcification, ill-defined margins, expansile remodelling of bone with endosteal scalloping to cortical destruction with soft tissue mass.
  • Micro:
    Wide range of differentiation. Common denominators:
    Production of cartilaginous matrix.
    Lack of bone/osteoid formation by tumour cells.
    Permeation of bone & invasion into soft tissues.
    Also:
    Lobulated growth (+/- rings of reactive bone).
    Myxoid change in the cartilaginous matrix.
    +/- Foci of necrosis
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8
Q

Two classifications of Chondrosarcoma (page 1766 Rosai)

A
  • 1ry: Arising de novo.
  • 2ry: Associated with a pre-existing benign condition. Eg. Osteochondroma.
  • Conventional
  • Variants:
  • Clear cell: Cells w abundant clear cytoplasm & sharply defined borders, large N w prominent nucleoli admixed w small trabeculae of woven bone/osteoid (not produced by the cells) & MN giant cells.
  • Myxoid: (> common in ST). Looks like chordoma. Rows of round to spindle cells separated by a myxoid background.
  • Dedifferentiated: Transition from a low grade CS to a high grade sarcomatous component (OS, MFH, UPS, Rhabdosarc, etc)
  • Mesenchymal: Rare, 2nd or 3rd decades. In extraosseous sites like orbit, paraspinal region, meninges or ST of extremities. In bone: axial skeleton or craniofacial bones. Biphasic pattern with areas of cellular cartilage (S100+) and population of small, undifferentiated round to spindle cells (CD99 +, S100 -). HPC vessels. Other IHC: SOX9 and Osteocalcin +.
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9
Q

Grading of Chondrosarcoma (page 1766 Rosai)

A

Grading based on cellularity and cytologic atypia, to a lesser degree mitotic activity (Overall uncommon).

  • Grade 1: Resembles normal cartilage or an enchondroma, mild atypia (but permeative).
  • Grade 2: > cellular, abundant myxoid stroma, > atypia (nuclear enlargement, hyerchromasia, binucleation).
  • Grade 3: High cellularity, marked atypia.
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10
Q

Molecular analysis Chondrosarcoma and variants

A
  • Central/conventional CS: IDH1 & IDH2 mutations common.
  • Clear cell CS: Chromosome 9 & 20 abnormalities.
  • Myxoid CS: EWSR1 & NR4A3 gene rearrangements.
  • Dediff CS: Overexpression of TP53 & HRAS.
  • Mesenchymal CS: HEY1-NCOA2 fusion
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11
Q

Variants of Osteosarcoma (page 1754- 1758)

A
  • Telangiectatic: Blood filled spaces separated by septae containing pleomorphic mononuclear &MNG cells with ++mitosis, +/- areas of necrosis. DD: ABC.
  • Small cell: Small, uniform round or spindled cells. Need to identify osteoid & exclude other high grade neoplasms. IHC: SATB2 +, CD99 -.
  • Paraosteal (most common variant): Originates from the surface of cortex. Posterior aspect of distal femur. Broad beams of ostoid in a hypocellular fibrous stroma with minimal atypia.
  • Low grade central (rare): Similar to paraosteal OS.
  • Periosteal: Less common. Encases the bone like a glove. Diaphysis location.
  • Osteosarcoma of jaw: approx 35yo. Body of mandible or alveolar ridge of maxilla.
  • Other: Osteoblastoma-like OS, Chondroblastoma-like OS, giant cell rich OS, Secondary OS (due to Paget diease, etc.
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12
Q

DD of Osteosarcoma

A

Depending of predominant pattern:

fracture callus, fibrous dysplasia, metastatic carcinoma, osteoblastoma, fibrosarcoma, chondrosarcoma, GCT.

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