Fibrous Cortical Defects The fibrous cortical defect is a very small metaphyseal lesion seenin long bones, typically around the knee joint in children. They areusually picked up on a routine radiograph as an incidental finding.They are considered dysplastic or hamartomatous lesions and arevery common, with about a 25% incidence in normal childrenaround the age of four to five years. As the child matures, thelesions will disappear by a process of skeletal remodeling and,in most cases, the diagnosis is obvious based on a simple radio-graphic study. Microscopically, the lesions are filled with benignfibroblastic cells forming collagen and usually demonstrate nomacrophage or inflammatory activity.
CLASSICCase #13016 year femalefibrous corticaldefect distal femur
Non-ossifying Fibroma The non-ossifying fibroma is considered to be a larger form of thefibrous cortical defect seen in the lower extremities of children.The lesions are usually eccentrically located but the larger ones canbecome more central. Radiographically, they have a soap-bubblyappearance with slight thinning and dilitation of the adjacentcortical structure. The diagnosis can usually be established by x-rayalone without biopsy. These lesions are a common cause for path-ologic fracture in children. They are usually asymptomatic untilthe day of injury. There can be multiple lesions in the same patient,similar to fibrous dysplasia, and can even be associated with café-au-laite skin lesions. Histologically, the lesion consists of benign fibrous tissuespeckled with giant cells, histiocytes, and occasional foam cellsand even cholesterol deposits. Treatment usually consists of curette-ment and bone grafting in high risk athletic males.
CLASSIC Case #13222 year female with non-ossifying fibroma proximal tibia
Fibrous Dysplasia Fibrous dysplasia of bone is a relatively common hamartomatousdevelopmental process in the skeletal system that can be eithermonostotic or polyostotic. In the case of polyostotic, there can alsobe endrocrine abnormalities such as precocious puberty in femaleswith the McCune-Albright syndrome. This condition occursprimarily in females and can be associated with café-au-laite spotson the skin which have a rough serrated edge compared to thesmooth edges in neurofibromatosis. The monostotic form has anappearance similar to non-ossifying fibroma except that the lyticcomponent has a typical smokey appearance caused by metaplasticbone formation in the fibrous tissue. In the more severe polyostoticform, representing only about 10% of fibrous dysplasia, the diseasetends to amplify on one side of the body more than the othercausing leg length discrepancy, especially when there is a character-istic chronic deformity of the proximal femur; referred to in the
literature as the shepherd’s crook deformity; that frequentlyrequires surgical correction. The most common locations for fibrous dysplasia are theproximal femur, followed by the tibia, humerus, ribs and,occasionally, caranio-facial anatomy. Other endrocrinopathiesassociated with polyostotic fibrous dysplasia include hyperpara-thyroidism, acromegaly, Cushing’s disease and, occasionally,hypophosphatemic osteomalacia. Occasionally, one will see softtissue myxomas with fibrous dysplasia which is referred to as theMazabraud’s syndrome. Radiographically, there will be diffusedysplastic changes throughout the involved bones with gradualdilation and thinning of the cortices, and a soap-bubbly appear-ance but with a smoky look compared to non-ossifing fibroma.Histologically, there is evidence of benign fibrous tissue matrixstudded with islands of metaplastic bone with a so-calledalphabet soup appearance but without osteoblastic rimming of the
trabeculae. Occasionally one will see macrophages, osteoclasts,foam cells and even cholesterol deposits similar to what is foundin non-ossifying fibroma. In approximately 1% of cases, there willbe a conversion to a secondary sarcoma in adult life that couldpresent as an osteosarcoma, or malignant fibrous histiocytoma oreven a chondrosarcoma. Treatment usually consists of corrective osteotomies for secondarydevelopmental deformities, along with bone grafting, includingfibular strut grafts and occasionally intramedullary devices to preventrepeated stress fractures. Recently there has been enthusiasm forthe use of biphosphonates to inhibit the osteoclastic activity ingrowing children that produces weakening of the bone. It is bestnot to perform bone grafting procedures in children because of thehigh recurrence rate in children under 16 years of age.
Desmoplastic Fibroma of Bone Desmoplastic fibroma of bone is an extremely aggressive, butbenign, fibrous lesion seen in long bones as well as the mandible.It represents 1% of all bone tumors and occurs typically in childrenand young adults with equal sex distribution. The long bonesinvolved include the distal femur, proximal tibia, proximalhumerus and the lower half of the pelvis. Radiographically, theselesions have an aggressive and moth-eaten appearance, erodinginto cortical bone and breaking out into the adjacent soft tissue,much like the low grade fibrosarcoma. Histologically, the tumorappears identical to aggressive fibromatosis seen in soft tissue withintense collagen formation by aggressive-appearing fibroblasts withan occasional mitotic figure. With curettement alone, the recurr-ence rate is very high, in the neighborhood of 40%, and for thisreason most authorities suggest a wide resection and possibleprosthetic replacement. This tumor will not metastasize to the lung.
CLASSICCase #13827 year femaledesmoplastic fibromadistal femur
Fibrosarcoma of Bone Fibrosarcoma of bone is a malignant spindle cell sarcoma seen inan older age group with a peak incidence in the fourth decade oflife. It is ten times less frequent than osteosarcoma but involvessimilar bones including the distal femur, proximal tibia, pelvis,proximal femur and proximal humerus. It is rare in the spine, handor foot. Radiographically, the fibrosarcoma has a permeative lyticappearance in the metaphyseal ends of long bones, similar to thatseen in lymphomas or malignant fibrous histiocytoma. Histo-logically, the tumor demonstrates aggressive fibroblastic activitywith collagen formation similar to what is seen in desmoplasticfibromas but with a much higher mitotic index. The lesions can below grade or high grade. The low grade lesions carry a goodprognosis with a low incidence of metastasis to the lung, whereasthe high grade lesions, just like with osteosarcoma, are moreaggressive with a worse prognosis and a higher potential for
metastasis. Treatment consists of wide local resection of the tumor,if possible. If the lesion is high grade, adjuvant therapies includinglocal radiation therapy and chemotherapy are frequently implementedto reduce the chance of pulmonary metastasis. Limb salvageprosthetic reconstructions are frequently utilized as in the case ofosteosarcoma.
CLASSICCase #14061 year malepathologic fracture thrufibrosarcoma distal femur
Malignant Fibrous Histiocytoma of Bone Malignant fibrous histiocytoma of bone is a relatively new patho-logical entity in bone tumors, compared to soft tissue tumorswhere malignant fibrous histiocytoma is a more common tumor.Malignant fibrous histiocytoma (MFH) of bone occurs in a middleor older age group, more commonly in males than females. It isfound typically in the same locations as fibrosarcoma or osteo-sarcoma, including the distal femur, proximal tibia, and proximalhumerus. Radiographically, it is an aggressive permeative lesionin metaphyseal bone with significant cortical destruction that canbreak out into the adjacent soft tissue. Histologically, there isevidence of malignant fibroblasts as well as atypical histiocytesand giant cells, exactly as we see in soft tissue MFH. Because thisis usually a high grade tumor, the prognosis is quite guarded witha high potential for metastasis to the lung, similar to fibrosarcomaand osteosarcoma. Treatment consists of a wide surgical resection
with prosthetic reconstruction when possible, along withadjuvant chemotherapy to reduce the chance of pulmonarymetastases.
CLASSIC Case #14226 year male with pathfracture thru MFHfemoral neck
Leiomyosarcoma of Bone Leiomyosarcoma of bone is an extremely rare diagnosis withfewer than 50 cases in the world literature. It occurs typically inmiddle to older age adults in the same location in the skeleton asfibrosarcoma, MFH, and osteosarcoma are found in; distal femur,proximal tibia and upper humerus. Radiographically, these lesionshave a permeative lytic appearance, similar to a lymphoma,withextensive cortical breakdown and extension into the surroundingsoft tissue. Histologically, the malignant spindle cells with collagenformation look like a fibrosarcoma or MFH so that the only waya diagnosis can be established is by using the specific immuno-histochemical staining for smooth muscle protein. Treatment usuallyconsists of wide surgical resection and prosthetic implantation.Because of the poor prognosis with high grade lesions, they arefrequently treated with adjuvant systemic chemotherapy andradiation which is not very effective, especially in old patients.
CLASSIC Case #144 69 year female with leiomysarcoma proximal humerus