Case report 830: Aneurysmal bone cyst.
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Biomedical subjects
Publications and source records attributed to H T Temple.
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Alveolar soft-part sarcomas are rare and seldom considered in the differential diagnosis of a soft-tissue mass. Thus, early clinical recognition can be elusive. The authors have identified several clinical and radiographic features of alveolar soft-part sarcoma, emphasizing the importance of magnetic resonance imaging in the preoperative diagnostic and staging workup. Accurate diagnosis and treatment of this unusual tumor requires clinical suspicion and clinicopathologic correlation with appropriate radiographic studies. If the clinical or radiographic interpretation is equivocal, early biopsy is essential to differentiate alveolar soft-part sarcoma from arteriovenous malformation.
Increasing use of MR to evaluate primary bone neoplasms has stimulated numerous articles on the initial assessment of these lesions. However, scant MR literature has been written about the postoperative MR appearance. We studied the MR appearance of lesions treated by curettage followed by packing with cancellous bone-chip allograft. We retrospectively reviewed the MR scans of 18 consecutive patients treated in this way. Pathologic diagnoses of these lesions were confirmed according to commonly accepted criteria. The allograft sites showed a distinctive pattern of speckled bright signal on T1-weighted images in eight cases. Thirteen of 18 grafts showed a whorled or speckled pattern of increased signal on the T2-weighted images. Only four allograft regions had predominantly low signal on both T1- and T2-weighted images. Two of 18 patients had recurrent tumor proved by open biopsy. MR images in these cases showed areas of homogeneous signal that replaced areas of speckled hyperintensity on both T1- and T2-weighted images. In both these recurrences the tumor had signal intensity similar to that seen on the preoperative MR study. We conclude that knowledge of the MR appearance of cancellous bone chip allografts is important to avoid misinterpreting areas of high signal on T1- or T2-weighted images as areas of recurrence of tumor and/or hemorrhage.
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Osteosarcoma is the most common primary malignant tumor of bone in adolescents and young adults. It accounts for approximately 15% of all primary bone tumors confirmed at biopsy. There are numerous types of primary osteosarcoma, including intramedullary (high grade, telangiectatic, low grade, small cell, osteosarcomatosis, and gnathic), surface (intracortical, parosteal, periosteal, and high-grade surface), and extraskeletal. Osteosarcoma may also occur as a secondary lesion in association with underlying benign conditions. The identification of osteoid matrix formation and aggressive characteristics usually allows prospective radiologic diagnosis of osteosarcoma. As with all bone tumors, differential diagnosis is best assessed with radiographs, whereas staging is performed with computed tomography or magnetic resonance imaging. Understanding and recognition of the variable appearances of the different varieties of osteosarcoma allow improved patient assessment and are vital for optimal clinical management including diagnosis, biopsy, staging, treatment, and follow-up.
Distinction of enchondroma versus intramedullary chondrosarcoma affecting the appendicular skeleton (proximal to the metacarpals and metatarsals) is a frequent diagnostic dilemma. The authors studied a large series of patients with these lesions (92 with enchondromas, 95 with chondrosarcomas) using statistical assessment of both clinical parameters and numerous radiologic manifestations on images from multiple modalities to identify differentiating features. Multiple clinical and imaging parameters demonstrated statistically significant differences between enchondroma and chondrosarcoma, particularly pain related to the lesion, deep endosteal scalloping (greater than two-thirds of cortical thickness), cortical destruction and soft-tissue mass (at computed tomography or magnetic resonance imaging), periosteal reaction (at radiography), and marked uptake of radionuclide (greater than the anterior iliac crest) at bone scintigraphy. All of these features strongly suggested the diagnosis of chondrosarcoma. These criteria allow distinction of appendicular enchondroma and chondrosarcoma in at least 90% of cases.
Numerous neurogenic tumors can affect the musculoskeletal system, including traumatic neuroma, Morton neuroma, neural fibrolipoma, nerve sheath ganglion, neurilemoma, neurofibroma, and malignant peripheral nerve sheath tumors (PNSTs). The diagnosis of neurogenic tumors can be suggested from their imaging appearances, including lesion shape and intrinsic imaging characteristics. It is also important to establish lesion location along a typical nerve distribution (eg, plantar digital nerve in Morton neuroma, median nerve in neural fibrolipoma, large nerve trunk in benign and malignant PNSTs). Traumatic and Morton neuromas are commonly related to an amputation stump or are located in the intermetatarsal space, respectively. Neural fibrolipomas show fat interspersed between nerve fascicles and are often associated with macrodactyly. Nerve sheath ganglion has a cystic appearance and commonly occurs about the knee. Radiologic characteristics of neurilemoma, neurofibroma, and malignant PNST at computed tomography (CT), ultrasonography, and magnetic resonance imaging include fusiform shape, identification of entering and exiting nerve, low attenuation at CT, target sign, fascicular sign, split-fat sign, and associated muscle atrophy. Although differentiation of neurilemoma from neurofibroma and of benign from malignant PNST is problematic, recognition of the radiologic appearances of neurogenic tumors often allows prospective diagnosis and improves clinical management of patients.
The musculoskeletal fibromatoses comprise a wide range of lesions with a common histopathologic appearance. They can be divided into two major groups: superficial and deep. The superficial fibromatoses are typically small, slow-growing lesions and include palmar fibromatosis, plantar fibromatosis, juvenile aponeurotic fibroma, and infantile digital fibroma. The deep fibromatoses are commonly large, may grow rapidly, and are more aggressive. They include infantile myofibromatosis, fibromatosis colli, extraabdominal desmoid tumor, and aggressive infantile fibromatosis. Radiographs typically reveal a nonspecific soft-tissue mass, and calcification is common only in juvenile aponeurotic fibroma. Advanced imaging (ultrasonography, computed tomography, and magnetic resonance [MR] imaging) demonstrates lesion extent. Involvement of adjacent structures is common, reflecting the infiltrative growth pattern often seen in these lesions. MR imaging may show characteristic features of prominent low to intermediate signal intensity and bands of low signal intensity representing highly collagenized tissue. However, fibromatoses with less collagen and more cellularity may have nonspecific high signal intensity on T2-weighted images. Local recurrence is frequent after surgical resection due to the aggressive lesion growth. It is important for radiologists to recognize the imaging characteristics of musculoskeletal fibromatoses to help guide the often difficult and protracted therapy and management of these lesions.
The radiologic features of giant cell tumor (GCT) and giant cell reparative granuloma (GCRG) of bone often strongly suggest the diagnosis and reflect their pathologic appearance. At radiography, GCT often demonstrates a metaepiphyseal location with extension to subchondral bone. GCRG has a similar appearance but most commonly affects the mandible, maxilla, hands, or feet. Computed tomography and magnetic resonance (MR) imaging are helpful in staging lesions, particularly in delineating soft-tissue extension. Cystic (secondary aneurysmal bone cyst) components are reported in 14% of GCTs. However, biopsy must be directed at the solid regions, which harbor diagnostic tissue. These solid components demonstrate low to intermediate signal intensity at T2-weighted MR imaging, a feature that can be helpful in diagnosis. Multiple GCTs, although rare, do occur and may be associated with Paget disease. Malignant GCT accounts for 5%-10% of all GCTs and is usually secondary to previous irradiation of benign GCT. Treatment of GCT usually consists of surgical resection. Recurrence is seen in 2%-25% of cases, and imaging is vital for early detection. Recognition of the spectrum of radiologic appearances of GCT and GCRG is important in allowing prospective diagnosis, guiding therapy, and facilitating early detection of recurrence.
Quadriceps muscle strains are common sporting injuries, but occasionally a tear of the rectus femoris muscle can appear as a soft tissue mass of the anterior thigh with or without a significant history of trauma. Between 1992 and 1996, seven patients were referred to the Orthopaedic Oncology Unit at Walter Reed Army Medical Center with an unexplained soft tissue mass of the thigh. Three were active duty soldiers, three were military dependents, and one was a retired serviceman. All patients were men, and the mean age was 32 years (range, 15 to 73). A palpable, mildly tender mass was confirmed on clinical examination. Laboratory studies and plain radiographs were normal. Magnetic resonance imaging showed an obvious, but often ill-defined, lesion at the musculotendinous junction of the rectus femoris muscle. Four patients subsequently underwent a tissue biopsy to rule out a soft tissue sarcoma. Histologic studies showed fibrosis, degeneration of muscle fibers, and chronic inflammatory cells with no evidence of malignancy. A chronic rectus femoris muscle tear can mimic a soft tissue tumor or sarcoma and needs to be excluded in the differential diagnosis. These tears may occur acutely or may represent an overuse injury caused by repeated microtrauma. Careful history taking, physical examination, and selective radiographic studies, specifically magnetic resonance imaging, can confirm the diagnosis of muscle tear and full functional recovery can be anticipated.
BACKGROUND: Soft-tissue tumors of the foot and ankle are relatively common and mostly benign. Thus, many malignant tumors in this region are improperly treated initially. Unplanned excisions can lead to complications that may adversely affect patient outcomes and prognosis. METHODS: A retrospective review of patients treated at our institute over a 20-year period for malignant soft-tissue tumors of the foot and ankle was performed. The effect of unplanned surgical excisions on outcomes was examined. RESULTS: When limb salvage was attempted, patients who underwent unplanned surgical excisions had more complications and more extensive surgical procedures involving free flaps, and they were more likely to require adjuvant radiotherapy. No difference in recurrence and disease-free survival was evident between the two patient populations. CONCLUSIONS: Despite the lack of statistical power to demonstrate differences in recurrence and survival, unplanned surgical excisions of soft-tissue sarcomas of the foot and ankle probably adversely affect quality of patient care. Suspicious lesions should be referred to surgeons trained in oncologic principles for evaluation and treatment.
A patient presented with a rapidly growing mass in the cervicothoracic paraspinous region. Associated clinical and radiographic skeletal abnormalities and histopathologic findings showing mild to moderate proliferation of spindle cells in a myxoid stroma led to the diagnosis of fibrodysplasia ossificans progressiva. Recognizing the clinical features of this disease is important and should avoid the need for obtaining tissue to make the diagnosis, because performing a biopsy may be particularly morbid in these patients.