Chondro-osseous tumours

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Bone occasionally crosses the desk of the pathologist. Primary bone tumours are rare; the most common bone tumour is metastases.[1]

Normal

  • Normal bone has osteocytes.
    • If the osteocytes are missing... the bone is dead.
  • Osteoblasts - make bone.
  • Osteoclasts - destroy bone.

Memory device: 'b' before 'c'.

Diagnosing bone tumours

  • Diagnosis should not be made without radiologic & clinical information.

Bone marrow

  • Fat content (%) ~= age (in years)[2]
    • e.g. 60 year old will have 60% fatty replacement.
  • Should see three cell lines.
    • The cell lines:[3]
      • Erythroid (red cells),
      • Myeloid (white blood cells),
      • Megakaryocytic (platelets).

Note: Lymphocytes are considered separately and typically spared in bone marrow failure.[4]

Identifying the lines:[5]

  1. Megakaryocytes:
    • Big cells ~ 3x the size of a RBC.
  2. Normoblasts (RBC precursors):
    • Hyperchromatic, i.e. blue, nucleus.
  3. Myeloid line:
    • Granules.
    • Reniform nucleus, i.e. kidney bean shaped nucleus.

Images:

Organization

  • Mature hematopoeitic cells at the centre (distant from bone).
  • Immature hematopoeitic cells adjacent to the bone.

Infectious

Osteomyelitis

General

  • Hematogenous - often in children.
  • Direct entry (skin defect) - adults with diabetes.

Micro.

  • PMNs.

Chronic osteomyelitis

  • Plasma cells.
    • May be sterile, i.e. no organisms.

Bone tumours

General:

  • Metastasis:primary bone tumours = >20:1.[6]

Giant cell tumour

General[7]

  • Approx. 5% of primary bone tumours.
  • Age 20-45 years.

Clinical

  • May present with joint pain, immobility.

Micro.

  • Mononuclear cells key feature.
  • Giant cells.

Chondrosarcoma

Micro

Features:[8]

  • Abnormal cartilage.
  • Nuclear atypia.
    • Nuclear clearing.
    • Nucleoli.

Ewing sarcoma

General

  • AKA EWS/PNET:
    • EWS = Ewing sarcoma.
    • PNET = Primative neuroectodermal tumour.
  • EWS and PNET were once thought to be different tumours.

Clinical

  • Painful.
  • Usually younger than 20 years.

Radiology

Features:[9]

  • Long bones, diaphyses.
  • Destructive.
  • "Onion-skin" periosteal reaction.

Microscopic

Classification:

  • Small blue cell tumour.

Features:[10]

  • Scant clear cytoplasm (contain glycogen - PAS +ve, PAS-D -ve).
  • Lack nucleoli.
  • Round small nucleus.

IHC

Features:[11]

  • CD99 +ve (plasma membrane staining).
  • CD45 -ve.
    • Done to r/o lymphoma.
  • +/-Neural markers (NSE, synaptophysin, CD57 (??? CD56 ???), S100).
  • +/-Cytokeratins.
  • Caveolin-1[12]
    • New kid on the block.

Notes:[13]

  • CD99 +ve (plasma membrane) tumours:
    • Lymphoblastic lymphoma/leukemia.
    • Angiomatoid fibrous histiocytoma.
    • Desmoplastic small round cell tumour.

Molecular diagnostics

Common features:

  • EWS/FLI-1 fusion gene formation due to translocation: t(11;22)(q24;q12).[14][15]
    • Often detected by RT-PCR (with EWS 5' and FLI-1 3' primers).

Notes:

  • The t(11;22)(q24;q12) is seen in ~90% of EWS/PNET... but also in:
    • Olfactory neuroblastoma.
    • Small cell osteogenic sarcoma.
    • Polyphenotypic tumours.
    • Rhbdomyosarcoma.
    • Neuroblastoma (possibly).
  • Several other translocations exist.

Pigmented villonodular synovitis

  • Commonly abbreviated: PVNS.
  • Course: benign.

Microscopy

Features:[16]

  • Subsynovial nodules composed of cells with:
    • Abundant cytoplasm.
    • Pale nuclei.
  • Multinucleated giant cells.
  • Hemosiderin-laden macrophages.
  • Foam cells.

Osteosarcoma

General

  • Terry Fox was afflicited by this tumour.

Definition

  • Tumour that makes osteoid.
    • Osteoid = (extracellular) organic component of bone, normally produced by osteoblasts (cells which make bone matrix).

Histology

  • Spindle cells with malignant features (e.g. nuclear membrane irregularies, marked nuclear

size differences, mitoses) surrounded by delicate strands of osteoid.

    • Osteoid on H&E: pink, homogenous, "glassy".
    • Tumours typically very cellular - when compared to normal bone.
  • Large (multinucleated) osteoclast-like giant cells may be seen.[17]

Adamantinoma

General

Features:[18]

  • Rare: < 1% of bone tumours.
  • 25-35 years old.
  • Tibia, fibula.
  • Benign, may be locally aggressive.
  • Cousin of ameloblastoma.[19]

Radiology

  • Intracortical, radiolucent.

Micro.

  • Fibrous tumour.

Common malignant

  • Osteosarcoma.
  • Chondrosarcoma.
  • Ewing's sarcoma.
  • Multiple myeloma.
  • Metastases.
    • Most common tumours metastatic to bone (mnemonic: BLT with Ketchup & Pickles):
      • Breast,
      • Liver,
      • Thyroid,
      • Kidney,
      • Prostate.

Epi.[20]

  • Osteosarcoma -> 2nd decade.
  • Ewing's ->5-20 yrs.
  • Chondrosarcoma -> from enchondroma or osteochrondroma -- patients over 40 yrs.
  • Multiple myeloma -> most common primary bone tumour in adults.

Malignant bone tumours by age

Most common by age:[21]

  • <1 year old - neuroblastoma.
  • 1-10 years old - Ewing's of tubular bones.
  • 10-30 years old - osteosarcoma, Ewing's of flat bones.
  • 30-40 years old - reticulum cell sarcoma, fibrosarcoma, parosteal osteosarcoma, malignant giant cell tumour, lymphoma.
  • >40 years old - mets, multiple myeloma, chondrosarcoma.

Benign aggressive bone tumours

  • Giant cell tumours.
  • Osteoblastoma.
    • Thought to be related to osteoid osteoma.
    • If in long bones often diaphyseal.

Ref.:[22][23]

Brown cell tumour

Etiology

  • Due to hyperparathyroidism - usually parathyroid adenoma.

Microscopy

  • Fibrosis.

Hypercalcemia DDx

Mnemonic GRIMED:[24]

  • Granulomatous disease (tuberculosis, sarcoidosis).
  • Renal disease.
  • Immobility.
  • Malignancy (esp. squamous cell carcinoma, plasmacytoma).
  • Endocrine (primary hyperparathyroidism - leads to brown cell tumour).
  • Drugs (thiazides ... others).

References

  1. ↑ WMSP P.632
  2. ↑ IAV 26 Feb 09
  3. ↑ http://emedicine.medscape.com/article/199003-overview
  4. ↑ http://emedicine.medscape.com/article/199003-overview
  5. ↑ http://upload.wikimedia.org/wikipedia/commons/6/69/Hematopoiesis_%28human%29_diagram.png
  6. ↑ WMSP P.632
  7. ↑ WMSP P.648
  8. ↑ IAV 26 Feb 09
  9. ↑ WMSP P.650
  10. ↑ PST. 22 February 2010.
  11. ↑ WMSP P.651
  12. ↑ PST. 22 February 2010.
  13. ↑ PST. 22 February 2010.
  14. ↑ URL: http://atlasgeneticsoncology.org/Tumors/Ewing5010.html. Accessed on: 23 February 2010.
  15. ↑ PMID: 3163261
  16. ↑ http://www.wheelessonline.com/ortho/pigmented_villonodular_synovitis
  17. ↑ Papalas JA, Balmer NN, Wallace C, Sangueeza OP (June 2009). "Ossifying dermatofibroma with osteoclast-like giant cells: report of a case and literature review". Am J Dermatopathol 31 (4): 379-83. doi:10.1097/DAD.0b013e3181966747. PMID 19461244.
  18. ↑ WMSP P.650.
  19. ↑ NEED REF.
  20. ↑ TN05 OR42
  21. ↑ TN05 OR42
  22. ↑ TN05 OR41
  23. ↑ http://www.emedicine.com/RADIO/topic494.htm
  24. ↑ TN06 Emerg

See also

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