A 10-year old boy presented with a mid tibial swelling. On X-ray, lytic lesion with sclerotic margins was seen. What is the most likely diagnosis?
Correct Answer: Osteoid osteoma
Description: Ans. a. Osteoid osteoma (Ref: Apley 9/e p194-204: Turek's 6/e p286)The most likely diagnosis in a 10-year-old boy who presents with a mid tibial swelling and lytic lesion with sclerotic margins on X-ray is osteoid osteoma.Non-ossifying Fibroma (Fibrous Cortical defect)* MC benign lesion of bone* A developmental defect in which a nest of fibrous tissue appears within the bone and persists for some years before ossifying.* Asymptomatic, almost always encountered in children as an incidental finding on X-ray.* MC sites: Metaphyses of long bones* X-ray: Oval radiolucent area surrounded by a thin margin of dense boneFibrous Dysplasia* MC sites: Proximal femur, tibia, humerus, ribs and cranio-facial bones.* X-ray: Radiolucent 'cystic' areas in the metaphysis or shaft; lucent patches typically have a slightly hazy or 'ground-glass' appearance.* The weight bearing bones may be bent, and one of the classic features is the 'shepherd's crook' deformity of the proximal femur.* Radioscintigraphy shows marked activity in the lesion.Osteoid Osteoma* This tiny bone tumour (<1 cm in diameter) causes symptoms out of all proportion to its size.* More common in males. <30 years of age.* Any bone except the skull may be affected, but over half the cases occur in the femur or tibia.* Persistent pain, typically relieved by salicylates.* If the diagnosis is delayed, other features appear: a limp or muscle wasting and weakness: spinal lesions may cause intense pain, muscle spasm and scoliosis.* X-ray: Small radiolucent area, the so-called 'nidus'. Lesions in the diaphysis are surrounded by dense sclerosis and cortical thickening; this may be so marked that the nidus can be seen only in fine cut CT scans. Lesions in the metaphysis show less cortical thickening.* Further away the bone may be osteoporotic. 99mTc-MDP scintigraphy reveals intense, localized activity.Eosinophilic Granuloma* It is a type of histiocytosis presenting as a pure bone lesion.* Marrow-containing bone is resorbed and one or more lytic lesions may appear in the flat bones or the metaphyses of long bones.* The patient is usually a child; there is seldom any complaint of pain* Discovered Incidentally or after a pathological fracture.* X-ray: Well-demarcated oval area of radiolucency within the bone; sometimes this is associated with marked reactive sclerosis.* There may be multiple lesions and in the skull they have a characteristic punched-out appearance.* Vertebral collapse may result In a flat wedge (vertebra plana), which is pathognomonic.Osteoid OsteomaOsteoid osteoma (sclerosing non-suppurative osteomyelitis of Garre or cortical bone abscess) is solitary, benign, osteoblastic, painful lesion of boneQ.There is no risk of malignant transformation.MC benign true bone tumorQAny bone except skull may be affected but most (> 50%) cases occur in metaphyseal or diaphyseal region of femur or tibiaQIf the lesion is in vertebral column, posterior element is most commonly involved.Pathology:Characterized by a nidus of osteoid tissue (with osteoblast, fibrovascular stroma, numerous non-myelinated neurons),which may be purely radiolucent or have a sclerotic centerNidus is often surrounded by a zone of dense reactive (sclerotic) bone formationClinical Features:Mostly occurs in children, adolescents or adults < 3(1 years oldQ, with male preponderanceQSymptoms are out of proportion to its size.Most important symptom is pain that is more severe at night and dramatically relieved by aspirin (or NSAID's)Q with in ~20-25 minutesLimp, muscle atrophy, secondary painful scoliosis with concavity of curvature usually on the side of lesion (d/t paravertebral spasm) and neurological signs may be other presentations.Diagnosis:Most of the tumors are intracortical, with nidus appearing as a radiolucent lesion.X-ray: Small radio lucent area (nidus) surrounded by dense sclerosis and cortical thickening, when the lesion is in diaphysisQOccasionally, diaphyseal lesions become so sclerotic that there is no radiological evidence of nidusQ. In these instances CT scan is procedure of choice to identify nidusTc 99 -- HDP scintigraphy reveal increased uptake in nidusQ and is of considerable value to make a correct diagnosis if osteoid osteoma is suspected but the lesion is not clearly demonstrated on plain X-ray.Treatment:Self-limiting lesion, mature spontaneously over the course of several yearsThe nidus gradually calcifies then ossifies to blend into sclerotic surrounding bone and pain diminishes, managed by salicylates or NSAlDs non-surgicallySurgery remains the standard treatment when histology is in doubt, or neurovascular structures are within 1.5 cm, or in repeated failure of any other minimally invasive ablative technique or percutaneous reaction.Open surgical techniques include en block resection (+ grafting and internal fixation) and bur-down (curettle)Q.Most Common Bone TumorsMC bone lesion* Fibrous cortical defect (non-ossifying fibroma)QMC bone tumor* SecondariesQMC site for secondaries* VertebraQMC benign bone tumor* OsteochondromaQMC true bone tumor* Osteoid osteomaQMC primary malignant tumor* Multiple myelomaQ
Category:
Orthopaedics
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