Chondrosarcoma of the femur with histology-imaging correlation of tumor growth--preliminary observations concerning periosteal new bone formation and soft tissue extension.

UNLABELLED: The objective of this study was, in chondrosarcoma (CHS) of the femur, to evaluate by radiologic-pathologic correlation, the degree of tumor growth, cortical destruction, periosteal reaction, and soft tissue extension present. MATERIALS AND METHODS: Eight cases of histologically proven CHS of the femur were studied. All cases were resected, evaluated histologically with coronal slabs, and compared with radiographs and magnetic resonance imaging (MRI) scans. In two resected specimens, the tumors were studied in more detail; along with coronal slabs, axial sections of the remaining anterior and posterior halves of both tumors were taken, and the bone specimens were X-rayed and examined histologically. RESULTS: CHS initially involved the medullary cavity and subsequently destroyed the cortex; first, by endosteal scalloping and, second, by subsequent invasion and destruction of the cortex. During this process, there was periosteal new bone formation (PNBF), with increased cortical thickness, the degree of which often correlated with the degree of cortical destruction. In the areas of cortical thickening of three cases, a "grey line" was seen on MRI that separated the cortex from the periosteal new bone; the line, in reality,is a space between the two structures. The presence of this line suggests that the tumor does not extend beyond the cortex. PNBF occurred in all cases and varied in thickness. It frequently developed independent of direct periosteal tumor involvement. The periosteum of one case contained porotic bone with interposed marrow fat, which was easily misinterpreted as tumor extension on MRI. Expansion and remodeling of the femoral diaphysis in CHS, with widening of the medullary cavity, is usually due to extensive cortical destruction with PNBF. Soft tissue extension was present in five cases and apparently occurred by two different mechanisms: direct tumor destruction of the cortex and periosteum, with extension into the soft tissues; and subtle MRI occult tumor permeation through the periosteum. As far as we know, a first literature histologic description of the thickened CHS periosteum also was accomplished. CONCLUSION: PNBF is a common imaging manifestation of CHS of the femur, which correlated with the degree of cortical destruction. A grey line between the cortex and periosteum is an MRI finding described in this study and may facilitate the evaluation of periosteal thickening and tumor invasion in CHS. PNBF often occurs in the absence of direct periosteal involvement. Periosteal imaging abnormalities suggestive of tumor infiltration should be interpreted with caution on MRI, and early soft tissue extension in CHS may be difficult to determine on MRI.

Glomus tumor of the thigh: confluent with the periosteum of the femur.

True glomus tumor is rare. In the majority of cases it involves the hand, preferring the fingertips or nail beds. We report a patient with glomus tumor of the mid-thigh who presented with severe localized pain and limp. The imaging features are discussed and the English literature reviewed.

Cystic degeneration of medullary bone infarction evaluated with magnetic resonance imaging correlated with pathologic examination.

OBJECTIVE: To evaluate the imaging pattern of cystic degeneration of medullary infarcts of the long bones. Medullary infarction of the long bones is a well-recognized entity. Cystic degeneration, however, is extremely rare and may frequently cause difficulty in the differential diagnosis. METHODS: We reviewed 15 cases of cystic degeneration of infarction of the long bones in 13 women and 2 men whose mean age was 41 (range 21-82) years. Conventional radiographs were obtained in every case. Eleven of the 15 cases were evaluated by magnetic resonance imaging (MRI). RESULTS: Six of the lesions occurred in the humerus, 5 in the femur, 2 in the tibia and 2 in the iliac bone. Fourteen patients presented with dull pain over the area; 1 patient was asymptomatic. The size of the lesions ranged between 1.5 cm and 12 cm in their greatest diameter. All of the 15 lesions proved to be benign on pathologic examination. On plain radiographs, about half of the lesions showed an expansile pattern and contained faint-to-dense calcifications. Using MRI, the lesions showed decreased signal intensity on T,-weighted imaging and appeared heterogeneously bright on T2-weighted imaging. After contrast injection, a well-defined unenhanced lesion was consistent with fluid collection. CONCLUSION: MRI is a valuable tool in diagnosing cystic degeneration of medullary infarction. Findings such as unenhanced lesions with well-defined margins are suggestive of fluid collection. The presence of dystrophic calcification and the thinned, but intact, cortex may suggest a benign underlying process such as medullary infarct.