Bone tumors

Osteosarcoma ( Osteogenic sarcoma)

• 2nd Most common Primary Bone Tumor

• Most common malignant bone tumor in children and adolescents

• Most common primary bone tumor causing Pulmonary metastasis

• Malignant tumor of mesenchymal cells

• Most common site - Medullary cavity of metaphysis of long bone ( Distal end of femur > Proximal end of tibia)

• Age - 2nd decade

• 2 Types of osteosarcoma - 

1) Primary osteosarcoma (15-25yrs) ; Not associated with premalignant conditions

2) Secondary osteosarcoma (45 yrs onwards) ; Associated with premalignant conditions like Paget's disease , Bone dysplasia's like Fibrous dysplasia , Irradiation of bone , Bone infarction , Survivors of Retinoblastoma

• Radiological findings - 

1) Sunburst appearance (Sunray / Fir-tree / Moth-eaten) 

Reason - 

a) Periosteal reaction

b) Due to New bone formation i.e.., Ossification and Calcification along rapidly growing blood vessels running with Sharpey's fibers

2) Codman's triangle 

Reason - Due to Periosteal elevation

• Diagnosis - Bone scan , MRI

• Treatment - 

1) Chemotherapy + Limb salvation therapy / Amputation + Chemotherapy

2) Osteosarcoma is highly Radioresistant

T-10 Protocol for osteosarcoma = HDMTX + VCR + DOX + BCD + / - CDDP

{HDMTX - High Dose MethoTreXate ; VCR - VinCRistine ; DOX - DOXorubicin ; BCD - Bleomycin , Cyclophosphamide , Dactinomycin / Actinomycin D ; CDDP - Cisplatin}

• Variants of osteosarcoma - 

1) Juxtacortical-Parosteal osteosarcoma - 

Lies directly on Cortical surface - (Juxtacortical) , But finally Cortex is destroyed and Medullary cavity is invaded 

Low grade fibroblastic osteosarcoma 

Better prognosis

X-ray - Easily diagnosed as it is densely ossified (Mineralized)

Treatment of choice - Wide surgical Enblock Excision / Amputation

2) Telangiectatic type osteosarcoma - Pulsating (due to high vascularity)

Ewing's sarcoma

• Highly malignant , Undifferentiated

• PNET Family - Belongs to Peripheral Neuroectodermal Tumors family

• t (11 : 22) - Due to Translocation of Chromosome 11 & 22

• Site - Diaphysis (Medullary cavity ) of Long Tubular Bones (Diaphysis of Femur , Fibula > Ilium > Tibia)

• Males (common) ; 10-20 yrs

• Metastasis - Lungs > Bone & Bone marrow

• Histopathology -

1) Sheets of small round blue cells (Blue cell tumor)

2) Pale clear cytoplasm (Due to presence of Glycogen)

3) Cytoplasm - PAS +ve (Periodic acid schiff) (due to intracellular glycogen) ; Diastase digestible , Reticulin -ve

• Radiological findings - 

  1) Principal finding - Mottled rarefaction of spongiosa with permeation of overlying cortex ( due to rapid bone destruction )

2) Onion peel appearance ( Laminated / Layered Periosteal new bone formation)

3) Soft tissue mass ( Indication that neoplasm perforated Cortex )

4) "Hair on end" Periosteal reaction

• Diagnosis -

Most definitive diagnostic test -

 Demonstration of common cytogenetic translocation by Karyotyping (or) RT-PCR detection of t (11 : 22)

t (11 : 22) > t (21:22) > t (7 : 22)

Immunohistochemical staining - MIC 2 gene product i.e.., p 30/32

• Treatment -

1) Highly Radiosensitive (Melts on radiotherapy)

2) Chemotherapy ( Much more effective ) - Vincristine , Actinomycin D , Adriamycin , Ifosfamide , Etoposide - 1yr

Note - Etoposide is included as treatment for Ewing's sarcoma but not included in "T-10" Protocol of osteosarcoma 

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