Ortho Points

Classification system of bone tumors- ENNEKING classification

As per BONE PART INVOLVED
All bone tumors in metaphysis except
Epiphyseal- GCT, Chondroblastoma
Diaphyseal- Ewings sarcoma, osteoblastoma/ osteoid osteoma, Fibrous dysplasia sometimes

As per AGE GROUP
All tumors occur in less than 20 years age group except
40-60 years- Hemangioma, Chondrosarcoma
20-40 years- GCT
Bimodal- Osteosarcoma
Also remember, Ewings age group is 5-15 years with second decade being more common

MOST COMMON SITES
Fibrous dysplasia- Neck of femur, flat bones
Simple bone cyst- Proximal humerus
ABC- Proximal femur
Enchondroma- Hand bones
Osteochondroma- Distal femur > Proximal tibia
Osteoid osteoma- Femur diaphysis > Tibia
Osteosarcoma- Distal femur
Chondrosarcoma- Proximal femur
Ewings sarcoma- Femur diaphysis > Flat bones
Chordoma (tumor of notochord remenants)- Sacrum
Admantinoma- Mandible

SOME INPORTANT ONE LINERS
M.C tumor of bone- Metastasis
M.C Primary tumor of bone- Multiple myeloma > Osteosarcoma
M.C Benign bone tumor- Osteochondroma
M.C true benign bone tumor- Osteoid osteoma
M.C lesion of bone- Fibrous cortical defect
Most common radiation induced tumor- Osteosarcoma > Fibrosarcoma > Malignant fibrous histiocytoma
Most radio and chemosensitive bone tumor- Ewing sarcoma
Tumor having night pains- Osteoid osteoma
Tumor showing diagnostic response to Aspirin/ NSAIDS- Osteoid osteoma
Commonest bone tumor of hand bones is Enshondroma
Codman’s tumor is- Chondroblastoma
Pulsatile bone tumors include Osteoclastoma (GCT), Telengiectatic osteosarcoma, Metastasis from medullary carcinoma thyroid and renal cell carcinoma.
Egg shell calcification is a clinical sign seen in- GCT
Cell of origin of Ewings sarcoma is- Mesenchymal/ Mesodermal
Mode of inheritance in Hereditary multiple exostosis is- Autosomal dominant

IMPORTANT X RAY SIGNS
Fibrous dysplasia- Ground glass appearance, Rind sign (sclerotic margin around tumor), Shephard crook deformity (collapse of medial part of femoral neck so that proximal femur becomes hook shaped)
Simple bone cyst- Fallen leaf sign (can be seen in ABC but less often)
Hemangioma- Corduroy appearance (Jail house sign), Polka dot pattern
Osteoid osteoma- Nidus > 1.5 cms
GCT- Soap bubble appearance
Osteosarcoma- Codman’s triangle, Sunray appearance (due to calcification along sharpey’s fibers)
Chondrosarcoma- Pop corn like calcification
Ewing sarcoma- Onion peel appearance (intense periosteal reaction in layers), Codman’s triangle
CAUSES OF VERTEBRAE PLANA
Langerhan cell histiocytosis (Most common is Eosinophilic granuloma, a sub type of LCH)
Ewing sarcoma
Lymphoma/ Leukemia
Gaucher’s Disease
Aneurysmal bone cyst
Infection- Spondylitis

SOME SYNDROMES
McCune Albright syndrome- Polyostotic fibrous dysplasia, Pre cocious puberty, Caif-a-lait spots
Mazabraud syndrome- Polyostotic fibrous dysplasia with intra mural myxomas
Diaphyseal achalasia- Multiple osteochondromatosis/ Hereditary multiple exostosis
Ollier’s disease- Multiple enchondromatosis
Maffuci syndrome- Ollier’s disease plus multiple cavernous hemnagiomas

IMPORTANT BIOPSY PATTERNS
Chondroblastoma- Chicken wire appearance
Malignant fibrous histiocytoma- Storiform pattern
Fibrosarcoma- Herring borne pattern
GCT VARIANTS (where giant cells are there on biopsy)- Chondroblastoma (closest), ABC, SBC, Osteosarcoma with giant cells, fibrous dysplasia, non-ossifying fibroma
Ewings sarcoma- Small round cells (Also seen in Lymphomas, neuroblastoma, pineoblastoma, medulloblastoma, retinoblastoma- so called Primitive neuro ectodermal tumors)
Biphasic pattern- Synovial cell sarcoma

IMPORTANT TUMOR MARKERS
Ewings sarcoma- trl 11;22 (present in 85% cases), CD-99 and MIC-2 gene positive
Synovial cell sarcoma- trl X;18
Remember, SYNOVIAL SARCOMA is a soft tissue tumor that does not have synovial origin despite its name. It is a rare but aggressive tumor that arises from tendon sheaths or joint capsules where there are multipotent stem cell rests that differentiate into mesenchymal as well as epithelial structures, hence a BIPHASIC TUMOR. It is characterized by trl (X;18). Excision is the treatment of choice.
Also know,
Metastasis can be blastic/ sclerotic or lytic. Blastic are seen in prostate carcinoma and seminoma while lytic are seen in Kidney, Thyroid and Lung malignancies. However, the most common metastasis to bone come from breast carcinoma (however, its prostate in males) and are mixed and most commonly affect the thoracic spine.
And not to forget these markers:
Bone Resorption :
• Pyridinoline
• Deoxypyridinoline
• Collagen Telopeptides
• Hydroxyproline
• TRAP (Tartarate resistant acid phosphatase)
Bone Formation :
• Bone specific Alkaline Phosphatase
• Serum Osteocalcin
• Carboxy terminal extension peptide of procollagen -1

EXTRA MARKS
(#) Prognostic factors for Ewings sarcoma- The most unfavorable prognostic factor in Ewing’s sarcoma is the presence of distant metastasis at diagnosis. Other unfavourable prognostic factors include an age older than 10 years, a size larger than 200 ml, more central lesions (as in the pelvis or spine), and poor response to chemotherapy. Patients with such lesions have a reduced chance of survival. The histological grade is of no prognostic significance, however, as all Ewing’s sarcomas are of high grade. Fever, anemia, and elevation of the number and values of WBC, ESR, and LDH have been reported to indicate more extensive disease and a poorer prognosis.
(#) Extra osseous osteosarcoma and ewing sarcoma are also known to occur. These generally involve older adults and have relatively bad prognosis as compared to the osseous counter parts. Most common site for extra osseous Ewings is para vertebral musculature and chest wall while its thigh for extra osseous osteosarcoma