DOI: 10.1148/rg.254045204
RadioGraphics 2005;25:1082-1086
© RSNA, 2005
Best Cases from the AFIP
Dedifferentiated Liposarcoma of Soft Tissue with High-Grade Osteosarcomatous Dedifferentiation1
Liyuan Yu, MD,
Sungmi Jung, MD,
Leonard Hojnowski, MD and
Timothy Damron, MD
1 From the Departments of Radiology (L.Y., L.H.), Pathology (S.J.), and Orthopedics (T.D.), State University of New York–Upstate Medical School, 750 E Adams St, Syracuse, NY 13210. Received November 24, 2004; revision requested January 3, 2005, and received February 16; accepted February 25. All authors have no financial relationships to disclose.
Address correspondence to L.Y. (e-mail: yul{at}upstate.edu).
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History
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A 59-year-old white woman presented with a painless soft-tissue mass of the left thigh that had been progressively enlarging for about 6 months. At physical examination, the left distal thigh was markedly larger than the right. The large firm mass was noted along the medial aspect of the left distal femur. The remainder of the physical examination findings were fairly unremarkable. Her medical history was significant for breast cancer, seizure disorder, diabetes mellitus, hypertension, and hypercholesterolemia. Results of laboratory evaluation including white blood cell count, electrolyte level, hemoglobin and hematocrit levels, platelet count, and liver function studies were all within normal limits.
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Imaging Findings
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The radiographs showed a heavily calcified large soft-tissue mass in the anteromedial aspect of the thigh and a cap-shaped lucent area of fat with focal calcifications or mineralization along the proximal aspect of the mass. The underlying femur was unremarkable in appearance (Fig 1).
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Figure 1. Frontal radiograph of the left thigh shows a large heavily ossified soft-tissue mass (arrow) in the anteromedial aspect of the thigh. There is a cap-shaped lucent area of fat with focal calcifications or mineralization (arrowhead) along the proximal aspect of the mass. The underlying femur is unremarkable.
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A bone scan was performed for staging, which demonstrated the large mass at the mid to distal left thigh with intense radiopharmaceutical uptake. There was less radionuclide uptake in the superior portion of the mass. There was no evidence of distant metastasis (Fig 2).
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Figure 2. Anterior bone scans show intense radiopharmaceutical uptake in the large mass at the mid to distal left thigh (arrow). There is less radionuclide uptake in the superior portion of the mass (arrowhead).
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Magnetic resonance (MR) imaging was performed. On axial spin-echo T1-weighted MR images, the large extraskeletal mass had heterogeneous signal intensity (Fig 3). Heterogeneous enhancement was noted after intravenous administration of gadolinium contrast material (Fig 4). The proximal component of the mass showed fat signal intensity on T1-weighted images and images obtained with a fat suppression technique (short inversion time inversion recovery [STIR]). A similar but less prominent finding was noted along the distal extent of the mass (Figs 5, 6). The imaging findings were most compatible with the diagnosis of a soft-tissue osteosarcoma with lipomatous components. An alternative differential diagnosis of liposarcoma with osteosarcomatous dedifferentiation was considered as well.
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Figure 5. Coronal T1-weighted MR image shows the lipomatous cap containing focal areas of bone formation or calcifications (arrow) proximal to the primary mass. A similar but less prominent finding is noted along the distal extent of the mass (arrowhead).
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Figure 6. Coronal inversion-recovery MR image shows the lipomatous caps proximal and distal to the large heterogeneous extraskeletal mass. The lipomatous caps demonstrate low signal intensity.
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A core biopsy was performed by the orthopedic surgeon using an 18-gauge Tru-cut biopsy needle. Multiple specimens were obtained through the largely ossified component of the mass, since it was considered to have the highest grade of malignancy. The lipomatous portions of the mass were not sampled to eliminate additional unnecessary biopsy procedures and to prevent possible field contamination of the lipomatous portions by the more malignant osteosarcomatous component. The biopsy revealed a high-grade extraskeletal osteogenic sarcoma. Initially, the patient received neoadjuvant chemotherapy according to the T-10 Memorial Sloan-Kettering Cancer Center (MSKCC) protocol with ifos-famide, Adriamycin (doxorubicin), mesna, and high-dose methotrexate.
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Pathologic Evaluation
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On completion of the chemotherapy, the patient underwent successful wide surgical excision. The mass was intramuscular in location. The gross specimen was 11 x 10 x 9.5 cm, tan-white, and bone producing and had lipomatous portions proximally and distally. The bony lesion showed focal hemorrhagic necrosis. The lipomatous components were sharply delineated, measured 6.8 cm in greatest dimension, and were tan-yellow, glistening, and gritty with scattered white mineralization but showed no hemorrhage or necrosis (Fig 7).
At histologic analysis, the lipomatous portion of the tumor showed relatively mature adipocytic proliferation divided by fibrocollagenous septa (Fig 8). Scattered hyperchromatic and bizarre as well as multinucleated stromal cells were identified, especially within the fibrous septa. However, no typical monovacuolated or multivacuolated lipoblasts were found in multiple sections. The bony portion of the tumor consisted of spindle or pleomorphic cells with hyperchromatic nuclei of occasional multinucleation (Fig 9). There were prominent eosinophilic nucleoli in the sclerotic bone and osteoid matrix. Necrotic foci were often observed.
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Figure 8. Photomicrograph (original magnification, x200; hematoxylin-eosin stain) of the lipomatous portion of the tumor shows scattered hyperchromatic and bizarre as well as multinucleated stromal cells (arrows), especially within the fibrous septa, but no typical monovacuolated or multivacuolated lipoblasts.
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Figure 9. Photomicrograph (original magnification, x 20; hematoxylin-eosin stain) of the osteosarcomatous portion of the tumor shows hyperchromatic atypical cells (arrows) in the osteoid matrix. A cartilage component is seen on the right.
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Rather than a soft-tissue osteosarcoma with lipomatous elements, as originally suspected from the imaging studies and core biopsy, the final diagnosis based on the entire specimen was liposarcoma with osteosarcomatous dedifferentiation.
After the surgery, the patient received postoperative brachytherapy and chemotherapy. As of this writing, there was no evidence of recurrence or residual disease after surgical resection.
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Discussion
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Liposarcoma is the second most common soft-tissue sarcoma (1). It is histologically divided into five types according to the most recent (2002) World Health Organization (WHO) classification: (a) well-differentiated, which includes the adipocytic, sclerosing, and inflammatory subtypes; (b) dedifferentiated; (c) myxoid; (d) round cell; and (e) pleomorphic (1). We present a case that demonstrates dedifferentiation of a liposarcoma to high-grade osteosarcoma in the muscle of the extremity. To our knowledge, only five examples of dedifferentiated liposarcoma of the soft tissues with high-grade osteosarcomatous dedifferentiation have been recognized (2–6).
Dedifferentiated liposarcoma represents a malignant adipocytic neoplasm showing transition from atypical lipomatous tumor or well-differentiated liposarcoma to nonlipogenic sarcoma of variable histologic grade, usually at least several millimeters in diameter. It can originate in a primary lesion or occur in a recurrent tumor (3,7). In about 90% of cases, the dedifferentiated components are high-grade fibrosarcoma or malignant fibrous histiocytoma. The remainder of the cases contain rhabdomyosarcoma, leiomyosarcoma, dermatofibrosarcoma protuberans, hemangio-pericytoma, angiosarcoma, and meningioma (3,7).
Dedifferentiation most commonly occurs within well-differentiated liposarcoma in the retroperitoneum and inguinal regions, but it may also be encountered in the deep soft tissues of the extremities (7). It behaves aggressively, with a local recurrence rate of 41%, a metastasis rate of 17%, and disease-related mortality of 28% (3). The most important prognostic factor is anatomic location, with retroperitoneal lesions having the worst clinical behavior, which could be because of a longer latent period in the well-differentiated components at these sites. In addition, it is often impossible to achieve a wide surgical excision margin in the retroperitoneum (1,3,6).
The radiologic appearance of dedifferentiated liposarcoma reflects the histologic coexistence of a well-delineated fatty tumor and a closely apposed nonlipomatous mass (8). Radiography or computed tomography is superior to MR imaging in delineating the tumor mineralization or possible cortical bone erosion or destruction, whereas MR imaging is helpful in demonstrating the fatty nature of the tumor. Chest radiography can be used as an initial screening study for pulmonary metastases. An early-phase bone scan may show a marked increase in radiopharmaceutical uptake (1).
On MR images, the nonfatty region often appears as a nonspecific juxtaposed focal masslike area with prolonged T1 and T2 relaxation times. On the other hand, the nonlipomatous component of well-differentiated liposarcomas often has thickened, irregular septa or a minor nodular lesion (9,10). In our case, because of the extensive ossification and dominating large size of the dedifferentiated component within the liposarcoma at imaging, the most likely diagnosis of soft-tissue osteosarcoma was suggested before biopsy. Nevertheless, a dedifferentiated liposarcoma with osteosarcomatous dedifferentiation was considered given the low-opacity fatty areas proximal and distal to the large ossified soft-tissue lesion.
This case report is instructive in suggesting that all well-differentiated liposarcomas of the deep soft tissues should be considered to be at risk to dedifferentiate, to be a high-grade tumor, and to have metastatic potential (2,4), although that risk varies with the location and duration of disease. Moreover, the dedifferentiated component of the liposarcoma can vary in size from small to large. The ossification or mineralization can be focal or quite extensive, as in our case. In certain situations, it is important that both the lipomatous and mineralized nonlipomatous areas undergo biopsy so that an incorrect diagnosis is not made. Imaging can be used to direct these biopsies.
However, in our case, the biopsy diagnosis of the lipomatous components was not clinically significant, since the target treatment has to focus on the high-grade large osteosarcomatous portion of the mass, rather than the liposarcomatous portions. Finally, it is worth noting that chemotherapy is often used in conjunction with wide surgical excision (radiation therapy has limited and debatable use) for treatment of osteosarcoma, whereas radiation therapy can be quite effective in shrinking the liposarcoma before wide surgical excision and is often indicated in cases in which excision is incomplete (1,11).
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Acknowledgments
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The authors thank Ajo John, MD, and John Hodgson for photographic assistance and Colin Poon, MD, PhD, for critical reading of the manuscript.
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References
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- Enzinger FM, Weiss SW. Soft tissue tumor. 4th ed. St Louis, Mo: Mosby–Year Book, 2001.
- Henricks WH, Chu YC, Goldblum JR, Weiss SW. Dedifferentiated liposarcoma: a clinicopathological analysis of 155 cases with a proposal for an expanded definition of dedifferentiation. Am J Surg Pathol
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- Ippolito V, Brien EW, Menendez LR, Mirra JM. Case report 797: "Dedifferentiated" lipoma-like liposarcoma of soft tissue with focal transformation to high-grade "sclerosing" osteosarcoma. Skeletal Radiol
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- Goldblum JR, Weiss SW. Soft tissue tumors. St Louis, Mo: Mosby, 2001; 641–693.
- Tateishi U, Hasegawa T, Beppu Y, Satake M, Moriyama N. Primary dedifferentiated liposarcoma of the retroperitoneum: prognostic significance of computed tomography and magnetic resonance imaging features. J Comput Assist Tomogr
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- Kransdorf MJ, Meis JM, Jelinek JS. Dedifferentiated liposarcoma of the extremities: imaging findings in four patients. AJR Am J Roentgenol
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- Jelinek JS, Kransdorf MJ, Shmookler BM, Aboulafia AJ, Malawer MM. Liposarcoma of the extremities: MR and CT findings in histologic subtypes. Radiology
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- Kulander BG, Bolen JW. Pathology of soft tissue sarcomas. In: Raaf JH, ed. Soft tissue sarcomas: diagnosis and treatment. St Louis, Mo: Year Book Medical, 1993; 113–121.
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History
Imaging Findings
