Chondroblastoma is an exceptional, primary bone neoplasm commonly incriminating long bones. Preponderantly, tumefaction arises within a singular bone.

Majority (75%) of chondroblastomas occur within long bones wherein tumefaction arises within locations such as epiphyseal region of proximal or distal femur, proximal humerus or proximal tibia. Metaphyseal region is exceptionally involved. Tumour may incriminate calvarium of elderly subjects. Additionally, sites such as pelvis, patella, skull, ribs, scapula and navicular or carpal bones may delineate the neoplasm.

Tumefaction is encountered within 10 years to 25 years or second decade to third decade. A mild male predominance is observed with male to female proportion of 2:112.

Chondroblastoma is posited to arise from cartilaginous germ cells or epiphyseal cartilage cells. Probably, multipotent mesenchymal cells or synovial cells of tendon sheath may engender the neoplasm 12.

Chondroblastoma depicts K36M genomic mutation commonly delineated within H3F3B gene and exceptionally within H3F3A gene 12.

Chondroblastoma is associated with pain within implicated tumour zone. Joint effusion may ensue in neoplasms occurring within articular cartilage or synovium 12.

Cytological assessment demonstrates aggregates of uniform, spherical to elliptical cells intermingled with multinucleated giant cells, encompassed within a dis-cohesive matrix 12.

Grossly, chondroblastoma is adherent to abutting bone and may be resected along with the bony segment. Usually, tumefaction is firm, well circumscribed, white to blue or grey and varies from 3 centimetres to 6 centimetres in magnitude 12.

Cut surface exhibits variable foci of calcification, necrosis or cystic areas. Upon curettage, reddish, friable neoplastic tissue is obtained.

Upon microscopy, tumefaction is significantly cellular and composed of sheets of spherical to polyhedral chondroblastic cells imbued with abundant, eosinophilic cytoplasm and well demarcated cellular perimeter. Intracytoplasmic glycogen granules are evident. Nuclei appear elliptical, hyper-lobulated and demonstrate nuclear grooves. Nuclear atypia appears insignificant 12.

Focal aggregates of spindle-shaped cells may be enunciated. Peri-cellular zones of ‘lace-like’ or ‘chicken wire’ calcification appear intermingled with degenerative chondroblasts. Eosinophilic foci of chondroid matrix are invariably discerned 12.

Focal mitotic activity, necrosis and osteoclast-like giant cells may be commingled with cellular zones. Besides, aneurysmal bone cyst-like modifications are commonly observed 12.

Upon ultrastructural examination, neoplastic cells simulate epiphyseal cartilage cells obtained with tissue culture and demonstrate prominent fibrous lamina with well defined cellular perimeter 12.

Musculoskeletal tumour society staging (MSTS) or Enneking staging system designates benign bone and cartilaginous neoplasms as

Latent lesion composed of neoplasms such as non ossifying fibroma, enchondroma

Active lesion comprised of tumefaction as aneurysmal bone cyst, unicameral bone cyst,

chondroblastoma, chondromyxoid fibroma

Aggressive lesions constituted of neoplastic proliferations as giant cell tumour of bone23.

Chondroblastoma is immune reactive to H3.3B (H3F3B), p.Lys36Met or K36M, S100 protein, DOG1 or SOX934. Chondroblastoma is immune non reactive to desmin and CD34.

Chondroblastoma requires segregation form neoplasms such as chondromyxoid fibroma, giant cell tumour of bone, aneurysmal bone cyst, chondroblastoma-like sarcoma, geode or intraosseous ganglion, clear cell chondrosarcoma or osteomyelitis34. Also, distinction may be necessitated from osteosarcoma, osteoblastoma, Brown’s tumour or osteoid osteoma 34.

Plain radiography with anterior posterior, lateral and oblique views, computerized tomography (CT) or magnetic resonance imaging (MRI) may be adopted to appropriately discern chondroblastoma. Open surgical tissue sampling or surgical curettage can be beneficially employed for appropriate tumour discernment.

Fine needle aspiration (FNA) cytology is not recommended and is uncommon employed 34.

Plain radiographs depict a well demarcated, radiolucent lesion circumscribed with an attenuated, sclerotic perimeter. Matrix calcification may or may not be observed34. Tumefaction is commonly exemplified as an eccentric, radiolucent lesion within epiphysis of long bones. However, tumour extension into metaphysis may ensue.

Computerized tomography (CT) exhibits matrix calcification and solid periosteal reaction34.

Magnetic resonance imaging (MRI) is optimal for delineating bone marrow oedema along with periosteal and soft tissue reaction. T2 weighted imaging exhibits variable signal intensity.

Surgical extermination or neoplastic curettage along with or in the absence of bone grafting is an optimal and recommended treatment strategy34.

Chondroblastoma is appropriately alleviated with surgical curettage. En bloc surgical resection or amputation of implicated limb is beneficial in treating advanced neoplasms34.

Chondroblastoma can manifest as a locally aggressive tumefaction. Tumour reoccurrence may variably ensue, contingent to site of tumour emergence34.

Pulmonary metastases are exceptionally discerned.q34.