Michael H. McGuire

Magnetic resonance imaging of lesions of synovial origin

Three patients with histologically differing lesions of synovial origin and two with synovial cysts, one of which was a dissecting popliteal cyst, were examined by magnetic resonance imaging (MR) and computerized tomography (CT). The three histologically proven synovial lesions were synovial sarcoma, diffuse giant cell tumor of tendon sheath, and synovial chondromatosis. In two of the five patients MR provided better anatomic and morphologic appreciation than CT, while in the others they were of equal value. CT demonstrated calcification in two of the lesions while on MR calcification could be identified in only one patient where it outlined the mass. MR did not demonstrate calcification in the substance of the diffuse giant cell tumor of tendon sheath. Coronal, transverse, and sagittal images of magnetic resonance graphically demonstrated the extent of the soft tissue masses and their relationship to bone, vessels, and soft tissue structures. Synovial sarcoma had a shorter T1 than diffuse giant cell tumor of tendon sheath (these two lesions being of comparable size) and also had a uniformly longer T2. The dissecting popliteal cyst showed the most intense signals on the T1 weighted images, while the uncomplicated synovial cyst showed a long T1. On the T2 weighted images, each type of cyst showed a long T2. The variance and overlap of intensity of MR signals suggest limited specificity in predicting the histologic nature of the synovial lesion.

Magnetic resonance imaging of soft tissue masses: an evaluation of fifty-three histologically proven tumors.

Fifty-three histologically confirmed soft tissue masses in 48 patients were evaluated by magnetic resonance imaging (MR) and computerized tomography (CT). Twenty-three of these were malignant, twenty-three benign and seven of intermediate malignancy (all aggressive fibromatosis). The two procedures were compared for sensitivity and delineation of masses, their relationship to important neurovascular structures, their potential for histological diagnoses, their relative roles in influencing the surgical approach and the preferred modality in the follow-up for detection of tumor recurrence. Both modalities have their relative strengths and weaknesses. However, the superior contrast resolution of magnetic resonance imaging, its demonstration of lesions not clearly identified by CT, its pluridirectional capabilities and its ability to demonstrate large soft tissue tumors in a single coronal or sagittal plane makes it the preferred initial modality for evaluation of the soft tissue tumor of uncertain etiology and also in the follow-up of these patients. Despite MRs superiority in anatomically staging soft tissue tumors it, like CT, is of limited value in characterizing soft tissue sarcomas.

Grading of bone tumors by analysis of nuclear DNA content using flow cytometry.

We studied 217 consecutive tumors of bone by flow cytometric analysis of nuclear DNA concentration after staining with propidium iodide. A diagnosis and histological grade (benign, low-grade, or high-grade sarcoma) were assigned to each tumor on the basis of staging data (with the exception of the forty-six giant-cell tumors, which, although indistinguishable histologically, were divided according to the flow cytometric pattern into two distinct groups), and we quantitatively studied the flow cytometry data to assess the percentages of cells in diploidy, tetraploidy, or aneuploidy. When compared, the mean values for the flow cytometric data for the three grades showed significant differences. Criteria were established for the three classes of tumors: for benign tumors, less than 11 per cent tetraploidy and no aneuploidy; for low-grade sarcomas, more than 11 per cent and less than 17 per cent tetraploidy, and no aneuploidy; and for high-grade tumors, either more than 17 per cent tetraploidy or aneuploidy. Tests for compliance for all groups of tumors (excluding the forty-six giant-cell tumors)--benign, low grade, or high grade--were significant for most of the benign lesions (with the exception of chondroblastoma and fibrous dysplasia) and for the high-grade sarcomas (with the exception of round-cell tumors). The low-grade sarcomas did far less well, based principally on the failure of the low-grade chondrosarcomas, chordomas, and adamantinomas to comply with the criteria. An attempt to assess the value of the system as a predictor of metastases showed that a low percentage of diploid cells (less than 75 per cent) and the presence of an aneuploid peak correlated statistically with the development of metastatic disease, but the usefulness of this observation could not be fully assessed because of multiple variables, associated principally with treatment.

Magnetic resonance imaging in planning limb-salvage surgery for primary malignant tumors of bone.

In defining the linear extent of a malignant tumor in a long bone, radiographs, computerized tomography, and scintigraphy are routinely employed, especially when non-ablative surgery is being considered. The drawbacks of these modalities in defining the true intracompartmental extent of disease within a bone can largely be overcome with the use of magnetic resonance imaging. We did a prospective analysis of magnetic resonance imaging in sixteen consecutive patients with a primary malignant tumor of a long bone, and it showed that this modality has clinical promise of being more precise than the other modalities in defining the true proximal and distal extent of a tumor in a long bone. Coronal images permit easier planning of surgical techniques for salvage of a limb using an allograft than do a multiplicity of transverse images.

High signal intensity soft tissue masses on T1 weighted pulsing sequences

On T1 weighted pulsing sequences, the majority of soft tissue masses are of low signal intensity and show high intensity signals on T2 weighting. There however is a subset of soft tissue masses of varied histology that shows high signal intensity on T1 weighted pulsing sequences. These masses have either fat or blood in their substance. Lipomatous and hemangiomatous lesions that did not show high-signal intensity on T1 weighting were also encountered and are discussed. Present experience with MRI of soft tissue masses suggests that there is a limited spectrum of entities that produce high-signal intensity T1 weighted soft tissue masses.

Magnetic resonance imaging of osteosarcoma.

Early magnetic resonance (MR) experience in the evaluation of 14 consecutive long bone intramedullary osteosarcomas demonstrates the need for T1 and T2 weighted pulsing sequences in the staging of this disease. Intramedullary disease is best depicted by coronal T1 weighted pulsing sequences and subtle extra-compartmental discase by T2 weighted axial imaging. Both high intensity and low intensity intra-medullary signals were noted on T2 weighting, while all T1 weighted pulsing sequences showed intra-medullary disease to have low signal intensity. Extraosseous tumor on T2 weighting usually had a high signal, and disease extent was therefore sharply demarcated from uninvolved muscle and its relationship to vessels confidently assessed. MR appears optimally suited for local staging of osteosarcoma, further enhancing the role of radiology in planning limbsalvage surgical techniques.

Synchronous multicentric desmoid tumors (aggressive fibromatosis) of the extremities

Synchronous multicentric aggressive fibromatosis does not appear to have been previously reported. Two such cases are described. The tumors were identified by magnetic resonance (MR) imaging. The incidence of synchronous multicentric aggressive fibromatosis is not known. It is anticipated that increased use of coronal MR imaging will reveal more tumors of this type, both synchronous and metachronous. In a patient with known or suspected aggressive fibromatosis, every other soft tissue nodule or mass in the same limb has to be regarded as an additional tumor of the same histology.

Computed tomography or magnetic resonance for evaluating the solitary tumor or tumor-like lesion of bone?

Following an abnormal radiograph, an initial 34 patients had both computed tomography (CT) and magnetic resonance (MR) to further characterize and stage a solitary tumor. This experience determined the choice between CT and MR in evaluating the next 55 solitary tumors. The choice of examination depends on the radiologists ability to characterize the lesion from the radiograph as to its morphology, matrix, and probable histologic nature. The anatomic location, in turn, frequently influences the ability to characterize the lesion. Lesions in long bones can almost always be successfully characterized by radiography and, in these instances, only the MR examination is required to stage the tumor. Radiographic characterization of tumors in flat bones such as the scapula, certain portions of ribs, vertebrae, and pelvis is often difficult or incomplete. In these cases, CT is the preferred initial examination, and if further staging is required to establish the relationship of the tumor to soft tissues or neurovascular structures, the MR examination is done. Because of MRs superiority in staging the tumor and CTs superiority in characterizing the lesion, the initial choice between the two examinations should depend on the radiologists ability to characterize the lesion from the radiograph. When radiographic depiction of tumor permits assessment of its morphology, matrix and probable histologic nature, (characterization) MR ought to be the next examination solely for staging purposes. It is the anatomic location of the tumor and the radiologists ability to characterize it that ought to govern the choice of the next examination. Surgical and histopathological findings were known in all patients in this study.

Case report 370

Fig. 1 A, B. The radiological features in these anteroposterior and lateral roentgenograms of the distal half of the left femur are those of considerable new bone, which appears to be tumor bone, involving the posterior half of the femur and growing extensively into the soft tissues. Multiple radiolucent lesions, mainly confluent in appearance, are noted in the medullary cavity of the femur, adjacent to and interspersed thruout the new bone formation

Case report 467

An 18-year-old woman was admitted to the hospital following attempted suicide and symptoms of depression. A chest radiograph showed a large posterior mediastinal mass (Fig. 1). Computerized tomography demonstrated a heterogenous mass of mixed density, free of calcification or ossification, associated with destruction of the left fourth rib posteriorly, adjacent to its articulation with the contiguous vertebra (Fig. 2). MR scans showed the spinal cord and thoracic aorta to be uninvolved. The mass had a low signal intensity on Tl-weighted pulsing sequences and a high signal on T2-weighted pulsing sequences (Figs. 3 and 4). A CT-guided biopsy of the soft tissue component of the tumor was carried out.