The signs of malignant transformation in osteochondroma are all except:
Ans. b. Weight loss (Ref: Campbell's 11/e pe p 860-62; Apley 8/e pe p 178-79, 139; Turek's 6/e pe p 288-89)Weight loss is not the sign of malignant transformation in osteochondroma.The signs of malignant transformation in osteochondroma:Increase in sizeIncrease in thickness of cartilage cap: Cartilaginous cap (best visualized on MRI) Thick, > 2 cm, tabulated, extending into soft tissues in chondrosarcoma (Malignant degeneration of a peripheral solitary osteochondroma leads to chondrosarcoma.)Pain: When malignant changes occur, the lesions become painful and show evidence of growth.CriteriaOsteochondromaChondrosarcomaContinuity of cortex and medullary cavity with parent bonePresentQGradual lossQTumor (external surface)Well demarcated and distinctIndistinct and fuzzyCartilaginous cap (best seen on MRI)< 1cm (thin)Q> 3 cm (thick)Q, lobulated, extended into soft tissueMatrix patternDense at periphery with solid cortexNormal cancellous bone centrallyPeriphery is granular with small areas of rarefaction and disorganized calcification. Blotchy areas of calcification with center of tumor with streaky densities extending peripherallyAdjacent soft tissueNormalLarge soft tissue masses containing disorganized areas of calcificationOsteochondroma (Osteocartilagenous Exostosis)MC benign bone tumorQ accounting for ~40% of all benign cases.Consists of a bony base or stalk with a cartilage capQ that projects from the normal bone away from a near by joint.Etiopathogenesis:Developmental disorder, instead of a neoplasmCaused by misdirected growth of a portion of physeal plate that is projected laterally and causing development of eccentric cartilage capped bony prominenceMetaphyseal area of any bone developing by endochondral ossificationQ may be involved.MC sites: Fast growing ends of long bonesQ (distal femur, proximal tibia, proximal humerus > distal radius, distal tibia, proximal and distal fibula)Also occur in flat bones of pelvis (ilium), scapula and ribsQ.May be solitary (more common) or multiple (diaphyseal aclasia or multiple hereditary exostosis/ Multiple hereditary osteochondromatosis).Trevor's Disease is osteochondroma on epiphyseal side of growth plate.Clinical Feature:Most become evident under 20 years with slight male preponderancePresent with lump or interference of tendon function, pain, growth disturbanceQ, of an extremity, compromised joint motion, abnormal cosmetic appearance or secondary impingement of soft tissuesCauses of sudden increase in pain in OsteochondromaFractureQ through stalk or pedunculated lesionSarcomatous changeBursitisQ of overlying bursaImpingement of neighboring structure e.g. nerve, muscle etc.Malignant degeneration may lead to chondrosarcomaQ, usually occurring in adult life.Evidence of Malignant Transformation to ChondrosarcomaPain and evidence of growth of long duration after skeletal maturityQCartilaginous cap thicker than 1 cm in adultQ (in child may be 2 - 3 cm thick)Cartilage cap > 8 cm diameterQFluffy out lineQIncreased uptake on bone scans after maturityQCT or MRI soft tissue mass or displacement of major neurovascular bundleQ.Diagnosis:Biopsy of a presumed chondrosarcoma before surgery may be of limited valueQ due to significant chances of non- representative biopsy and a potential risk of seeding the biopsy tract.Classical feature: Cortex and cancellous bone of osteochondroma blend with the cortex and cancellous bone of hostQX-ray: Larger lesions undergo cartilage degeneration and calcificationSlight metaphyseal widening at the site of exostosis.TreatmentExcision of OC should, if possible, be postponed until later adolescence due to risk of recurrence and growth arrestQPrognosis:Prognosis following excision of chondrosarcoma is excellentQ
Pain
Weight loss
Increase in size
Increase in thickness of cartilage cap
Bone Tumour