OPBSPathologyVigorita appendices III and IV
Immunohistochemistry and molecular tests identify cell lineage and tumour specific genetic changes that routine light microscopy cannot. Exam questions pair each tumour with its marker or translocation.
Must Know
- Immunoperoxidase staining applies an antibody to a known antigen, bridges it with peroxidase antiperoxidase and shows a brown colour.
- Sarcoma genetics fall into three groups. Simple karyotypes with specific translocations, specific mutations or amplifications, and complex unstable karyotypes.
- Translocation group. Ewing sarcoma, synovial sarcoma and aneurysmal bone cyst.
- Mutation or amplification group. Chordoma and fibrous dysplasia.
- Complex karyotype group. Osteosarcoma.
- FISH works on nondividing interphase nuclei, so fresh, frozen or paraffin material can be used.
- RT-PCR is preferred when fresh frozen tissue exists, because RNA survives better.
- Somatic mutations, as in aneurysmal bone cyst and fibrous dysplasia, affect only descendants of the mutated cell.
- Germline mutations, as in X-linked hypophosphataemic rickets, can pass to offspring.
- Molecular workflow runs biopsy, neutral buffered formalin, paraffin, tumour selection on light microscopy, DNA or RNA extraction, then analysis.
Translocations and Karyotype Changes
| Tumour | Change | Frequency |
|---|---|---|
| Ewing sarcoma | t(11,22)(q24,q12) | 85 to 95 percent |
| Ewing sarcoma variant | t(21,22)(q22,q12) | 5 to 10 percent |
| Synovial sarcoma | t(X,18)(p11.2,p11.2) | Over 90 percent |
| Myxoid liposarcoma | t(12,16)(q13,p11) | Over 95 percent |
| Alveolar rhabdomyosarcoma | t(2,13)(q35,q14) | Over 70 percent |
| Alveolar rhabdomyosarcoma | t(1,13)(p36,q14) | 10 to 20 percent |
| Embryonal rhabdomyosarcoma | Trisomy 2q, 8 or 20 | Over 75 percent |
| Desmoplastic small round cell tumour | t(11,22)(p13,q12) | Over 95 percent |
| Alveolar soft part sarcoma | t(X,17)(p11,q25) | Over 90 percent |
| Clear cell sarcoma | t(12,22)(q13,q12) | About 90 percent |
| Dermatofibrosarcoma protuberans | Ring chromosome, t(17,22) | Over 99 percent |
| Infantile fibrosarcoma | t(12,15)(p13,q25) | Over 75 percent |
| Tenosynovial giant cell tumour | t(1,2)(p11,q35 to 37) | About 40 percent |
| Neuroblastoma | Hyperdiploidy, 1p deletion | Over 90 percent |
| Extraskeletal myxoid chondrosarcoma | t(9,22), t(9,17) or t(9,15) | Not stated |
| Low grade fibromyxoid sarcoma | t(7,16)(q34,q11) | Not stated |
| Parosteal osteosarcoma | Ring chromosome | Not stated |
| Giant cell tumour of bone | Telomeric associations | Not stated |
| Desmoid tumour | 5q21 to 22 | Not stated |
More on lymphoma and other changes
- Non-Hodgkin lymphoma translocations include t(8,14), t(14,18) and t(11,14).
- Intramuscular lipoma can carry a ring chromosome. Lipoma often shows 12q14 rearrangement.
- Wilms tumour shows deletion at 11p13.
Immunohistochemistry Panels
| Marker | Main use |
|---|---|
| CD99 (MIC2 product) | Ewing family of tumours |
| CD1a with S100 | Langerhans cell histiocytosis |
| CD31 | Endothelial differentiation |
| CD34 | Stromal tumours, endothelial stem cells, dendritic cells |
| CD38 and CD138, CD45 negative | Plasma cells and myeloma |
| CD20, CD79a | B cell lymphoma |
| CD3 | T cells, T lymphoblastic lymphoma |
| CD15, CD30 | Hodgkin lymphoma. CD30 also in anaplastic large cell lymphoma |
| CD117 | Mast cells, gastrointestinal stromal tumour |
| CD56 | Some primitive round cell tumours and sarcomas, neuroendocrine tumours |
| Primary site of a bone metastasis | Markers |
|---|---|
| Breast | GATA3, ER, GCDFP-15, mammaglobin |
| Lung adenocarcinoma | TTF1, napsin A |
| Prostate | PSA, PSAP, NKX3.1, ERG |
| Thyroid follicular | TTF1, PAX8, thyroglobulin |
| Clear cell renal | PAX8, PAX2, RCC marker, CD10, pVHL |
| Lower gut | CDX2, SATB2, CK20, CDH17 |
| Squamous carcinoma | p40, p63, CK5/6 |
| Melanoma | S100, HMB-45, MART-1, SOX10, MiTF |
| Neuroendocrine | Chromogranin, synaptophysin, CD56 |
- Synovial sarcoma expresses TLE1 and cytokeratin.
- Mesothelial cells express calretinin, WT1, D2-40 (podoplanin) and CK5/6.
- CD43 stains neoplastic B cells but not normal B cells.
Numbers to Remember
- Ewing sarcoma. t(11,22) in 85 to 95 percent, t(21,22) in 5 to 10 percent.
- Synovial sarcoma. t(X,18) in over 90 percent.
- Myxoid liposarcoma. t(12,16) in over 95 percent.
- Alveolar rhabdomyosarcoma. t(2,13) in over 70 percent, t(1,13) in 10 to 20 percent.
- Dermatofibrosarcoma protuberans. Ring chromosome in over 99 percent.
Memory Aids
- X marks synovial. Synovial sarcoma t(X,18).
- Eleven and twenty two for Ewing. Desmoplastic round cell tumour uses the same pair at 11p13.
- Two and thirteen, alveolar. Embryonal rhabdomyosarcoma has trisomies instead.
Exam Traps
- Desmoplastic small round cell tumour also joins chromosomes 11 and 22, but at 11p13 with no 11q24 break.
- Osteosarcoma has no single defining translocation. Its karyotype is complex and unstable.
- Clear cell sarcoma t(12,22) is a soft tissue tumour, distinct from clear cell chondrosarcoma.
- Plasma cells are CD38 positive and CD45 negative.
- Fibrous dysplasia and aneurysmal bone cyst mutations are somatic and not inherited.
Source
Vigorita VJ, Ghelman B, Mintz D. Appendix III, Immunohistochemistry or Immunoperoxidase Staining, and Appendix IV, Characteristic Genetic Abnormalities. In. Vigorita VJ, Ghelman B, Mintz D. Orthopaedic Pathology. 3rd ed. Philadelphia, Wolters Kluwer, 2016.
Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 17 October 2026.