pathology/8077/tumoral-calcinosisExplanation:PAROSTEAL OSTEOSARCOMAIt is a low-grade sarcoma situated on the surface of one of the tubular bones, usually at the distal femoral or proximal tibial metaphysis or proximal humeral metaphysis.The patient is a young adult who presents with a slowly enlarging mass near the hone end.X-ray shows a dense bony mass on the surface of the bone or encircling it; the cortex is not eroded and usually a thin gap remains between cortex and tumour.CT and MRI will show the boundary between tumour and surrounding soft tissues.Although the lesion is outside the bone, it does not spread into the adjacent muscle compartment until fairly late.Staging, therefore, often defines it as a low grade intracompartmental tumour (stage IA).The described clinical fits this best.PERIOSTE AL OSTEOSARCOMAIt is a rare tumour is quite distinct from parosteal osteosarcoma.It is more like an intramedullary osteosarcoma, hut situated on the surface of the bone.It occurs in young adults and causes local pain and swelling.X-ray shows a superficial defect of the cortex, but CT and MRI may reveal a larger soft-tissue mass. The appearances sometimes suggest a periosteal chondroma and the diagnosis may not be certain until a biopsy is performed.Histologically this is a true osteosarcoma, hut characteristically the sections show a prominent cartilaginous element.Myositis OssificansHeterotopic ossification in the muscles sometimes occurs after an injury, articularly dislocation of the elbow or a blow to the hrachialis, deltoid or quadriceps.It is thought to be due to muscle damage, hut it also occurs without a local injury in unconscious or paraplegic patients.It also occurs in hip injuries, after hip surgeries (THR) and burns patients.There may be a history of native massage treatment with passive manipulation.Soon after the injury, the patient (usually a fit young man) complains of pain: there is local swelling and soft-tissue tenderness.X-rav is normal but a bone scan may show increased activity.Over the next 2-3 weeks the pain gradually subsides, but joint movement is limited; X-ray may show fluffy calcification in the soft tissues.By 8 weeks the bony mass is easily palpable and is clearly defined in the X-ray.Above scenario is not falling into this choice.Tumoral calcinosisIt is a rare and poorly understood entity characterized by calcium salt deposits in the extra-capsular soft tissues.More common in females and African- Americans.Onset is usually in childhood or early adolescence.Typically occurs around joints, primarily the hip shoulder and elbows.Pathophysiology - is unknown.There is evidence suggesting an inborn abnormality of phosphorus metabolism.Associated conditions - calcinosis of renal failure, radiographically similar appearance to tumoral calcinosis, but not as strongly associated with hip and shoulder distribution.Renal aetiology differentiates it from tumoral calcinosis.Associated with hyperphosphatemia, chronic renal failure, and long term dialysisSymptoms - mass or swelling typically around joints, pain secondary to compression of normal, surrounding structures, palpable mass around jointImagingRadiographs - circular or oval, well- demarcated masses of calcium around joints, direct involvement of the bones or joints is rare.CT may demonstrate fluid-fluid levels within some of these massesMRI may demonstrate fluid-fluid levels within some of these masses.Bone scan may reveal intense uptake in the calcific masses.">