GIANT CELL VARIANTS DR. syed imran

Definition The tumors which histologicaly show giant cells. Multinucleated osteoclastic giant cells intermixed throughout a spindle cell stroma

Differential Diagnosis Osteoclastoma Aneurysmal Bone Cyst Chondroblastoma Unicameral Bone Cyst Chondromyxoid Fibroma Non-osteogenic Fibroma Fibrous Dysplasia Brown Tumor of Hyperparathyroidism

Osteoclastoma Most common bone tumour in the young adults aged 25 to 40. Most often the distal femur, proximal tibia, and distal radius. Giant cell tumour of bone is a benign lesion that is a usually solitary and locally aggressive. It is believed by some to be potentially malignant.

Radiology

Characteristic X-Ray finding of Giant Cell Tumour Solitary expansile lytic lesion Location: Metaphyseal and Juxta-articular (adjacent to joint). Multiple septation (soap bubble appearance). No reactive sclerosis. No periosteal reaction in absence of fracture.

Histology Microscopically, there are numerous multinucleated giant cells. The stromal cells are homogeneous mononuclear cells with round or ovoid shapes, large nuclei and indistinct nucleoli. The nuclei of the stromal cells are identical to the nuclei in the giant cells, a feature that distinguishes giant cell tumors from other lesions that also contained giant cells.

Treatment Surgery only. Intralesional excision by "extended" curettage is the treatment of choice. Addition of chemical cautery using phenol, multiple freeze-thaw cycles using liquid nitrogen, and treating the walls of the cavity with a high-speed rotary burr. Tumor cavity may be filled with polymethyl methacrylate cement or bone graft.

Aneurysmal Bone Cyst ABC is found most commonly during the second decade. ABC's can be found in any bone in the body.

Etiology True cause is unknown. A reactive lesion that may be caused by a local arteriovenous malformation or vascular injury. A definite relationship to local trauma in some cases, and other cases are associated with another tumor such as osteoblastoma, chondroblastoma, fibrous dysplasia, or other.

Radiology Hallmark is ballooned-out appearance. Eccentric location. Marked cortical thinning and erosion and periosteal elevation. Buttress of periosteal reaction (to differentiate from simple bone cyst) Usual containment by a thin shell of periosteum. Lesion rarely penetrates the articular surface or growth plate. CT scan and MRI can narrow the differential diagnosis of ABC by demonstrating multiple fluid-fluid levels within the cystic spaces..

Histology ABC is like a blood filled sponge with a thin periosteal membrane. Soft, fibrous walls separate spaces filled with friable blood clot. Microscopically, the ABC has cystic spaces filled with blood.

Treatment Curettage is normally used. Large lesions may require other treatments, such as embolization.

Chondroblastoma Chondroblastoma is a rare, benign tumor derived from chondroblasts. Found in the epiphysis of long bones, usually of the lower extremity. Most common site is the distal femur followed by the proximal femur, proximal humerus and proximal tibia.

Tumour has a preference for males over females and the mean age of presentation is approximately 20 years old. Chondroblastomas are radiolucent lesions that typically occupy the epiphysis (or apophysis) of long bones. They tend to be small (< 4 cm) with most exhibiting a sclerotic border.

CT is also useful for defining the relationship of the tumor to the joint, integrity of the cortex, and intralesional calcifications.

Histology A chondroblastoma has a lobulated, round form and is made up of friable, soft, grayish pink tissue that may be gritty. A scant chondroid matrix may be superimposed by a pericellular deposit of calcification that appears like "chicken-wire".

Treatment Biopsy and curettage with possible use of adjuvant liquid nitrogen or phenol, or a mechanical burr.

Unicameral Bone Cyst Unicameral bone cysts (UBC), also known as simple bone cysts, are lesions that consist of a fluid filled cavity lined by a thin membrane. Found in the metaphysis of long bones, with the most common site being the proximal humerus, followed by the proximal femur. "Active" cysts are located near the epiphysis .

Most commonly in children between the ages of ages 5 to 20 years old, and the ratio of male to female is 2:1. UBC's are asymptomatic and only present when a pathological fracture occurs.

Radiology Lesion appears as a well defined osteolytic area with a thin sclerotic margin. Lesion is relatively symmetrical with respect to the midline axis of the bone. The lesion is not eccentric and does not break out through the cortex or form any extra osseous mass.

A fragment of cortex that has fallen into a dependent position inside the cyst is known as the "fallen leaf" or "fallen fragment" sign.

Treatment When the lesion presents with a pathological fracture, closed treatment of the fracture is the first priority. Surgical treatment is sometimes necessary for lesions that are large or where the bone is weakened and pathological fracture must be treated or prevented.

Chondromyxoid Fibroma A benign cartilage tumor that also has myxoid and fibrous elements. Extremely rare. Metaphysis around the knee in the proximal tibia, proximal fibula, or distal femur.

Radiology Eccentrically placed Iytic lesion with well defined margins in the metaphysis of the lower extremity. Lesion usually has a sclerotic margin of bone and a lobulated contour.

Treatment En bloc resection.

Fibrous Dysplasia Uncommon, benign disorder characterized by a tumour-like proliferation of fibro-osseous tissue. Fibrous dysplasia can present as an autosomal dominant disorder affecting the mandible and maxilla bones in children in their teenage years.

Pathology The tissue in the tumor is immature, woven bone that cannot differentiate in to mature, lamellar bone. A mutation in a cell surface protein. Cells have an increased number of hormone receptors, which may explain why these lesions become more active during pregnancy.

Combination of polyostotic fibrous dysplasia, precocious puberty, and cafe au lait spots is called Albright's syndrome. Endocrine abnormalities including hyperthyroidism, Cushing's disease, thyromegaly, hypophosphatemia, and hyperprolactinemia have been associated with fibrous dysplasia.

Sphered crook deformity. Repeated fractures through lesions in the proximal femur can result in the formation of a so-called shepherd's crook deformity.

Fibrous dysplasia appears as a well circumscribed lesion in a long bone with a ground glass or hazy appearance of the matrix.

Histology Microscopically, fibrous dysplasia appears as irregular foci of woven bone arising from a cellular fibrous stroma. The stroma has a whorled appearance and is highly vascular. No lamellar bone is found within a fibrous dysplasia lesion.

Treatment Surgery is not necessary for an asymptomatic lesion unless there is a risk for pathological fracture. Surgery with curettage of the lesion can be associated with high rates of local recurrence. Painful long bone lesions can be stabilized by cortical grafting or implant fixation.

Cortical strut grafts are preferred to a morselized cortical cancellous grafts, which can become replaced with the same immature fibrous lamellar bone that comprised the lesion. Rigid, intramedullary fixation with the strongest possible device (a steel or titanium cephalomedullary nail) is the best method for treatment of proximal femoral lesions.

Brown Tumour Diffuse and focal lesions may arise in multiple bones. Skeletal effects include massive bone resorption, bone fractures, and bone pain, as well as diffuse osteopenia, or circumscribed lytic lesions. Undiagnosed hyperparathyroidism presents with a lytic lesion that may be mistaken for a tumor.

Radiology Presents as diffuse osteopenia as well as circumscribed lucent areas. Erosion of the tufts of the phalanges is an associated finding and is more pronounced on the radial aspect than the ulnar. "salt and pepper" skull.

Treatment Depends on the etiology of the condition. The tumors resolve once the abnormal metabolic condition is controlled.

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