DOI: 10.1148/radiol.2373031389
(Radiology 2005;237:880-883.)
© RSNA, 2005
Case 89: Retroperitoneal Extraskeletal Osteosarcoma1
Mustafa Secil, MD,
Ugur Mungan, MD,
Kutsal Yorukoglu, MD and
Oguz Dicle, MD
1 From the Departments of Radiology (M.S., O.D.), Urology (U.M.), and Pathology (K.Y.), Dokuz Eylul University Faculty of Medicine, 35340 Inciralti, Izmir, Turkey. Received August 28, 2003; revision requested November 11; final revision received February 13, 2004; accepted March 16.
Correspondence: Address correspondence to M.S. (e-mail: mustafa.secil{at}deu.edu.tr).
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HISTORY
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A 74-year-old woman presented with dull nonradiating pain in the right lumbar area that had worsened in the past 2 months. There was no accompanying fever, chills, nausea, vomiting, hematuria, hematemesis, diarrhea, or constipation. Past history included right pyelolithotomy 42 years previously followed by simple right nephrectomy in 1982 for a nonneoplastic abnormality (ie, nonfunctioning kidney, as stated by the patient). The patient had diabetes mellitus, which was under medical control, and no other known systemic illness existed. Physical examination of the patient revealed a firm mass on palpation of the right lumbar region. Findings of laboratory examinations were unremarkable, apart from elevated glucose and alkaline phosphatase levels. In this patient, the level of glucose was 119 mg/dL (6.6 mmol/L) (normal range, 70–110 mg/dL [3.9–6.1 mmol/L]), and the level of alkaline phosphatase was 1420 U/L (normal range, 34–270 U/L). Abdominal computed tomography (CT) was performed after administration of oral and intravenous contrast material. The patient was further evaluated with magnetic resonance (MR) imaging.
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IMAGING FINDINGS
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Abdominal CT revealed a soft-tissue mass in the right renal area (Fig 1). The mass had irregular margins, with invasion into the right psoas and quadratus lumborum muscles and diaphragmatic crus on the posterior and medial borders of the tumor. The adjacent vertebral body was spared, unlike the transverse process. Anteriorly, it produced a mass effect on the inferior vena cava and was in close contact with the liver. The internal structure of the mass was homogeneous, apart from the centrally located amorphous high-attenuation areas; this finding was consistent with calcifications. There was no fat inside the lesion.
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Figure 1. Transverse CT image of the abdomen obtained after administration of oral and intravenous contrast material shows a retroperitoneal soft-tissue tumor, with central high-attenuation areas (black arrows). The mass has invaded the right psoas and quadratus lumborum muscles (white arrows) posteriorly.
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The mass was of intermediate signal intensity on MR images (Figs 2, 3a). The soft-tissue component of the mass was moderately heterogeneous, without evidence of necrosis, hemorrhage, or a myxoid component. The central areas of high attenuation that were observed on CT images were hypointense on MR images, particularly on T1-weighted gradient-echo images, and their appearance was consistent with that of calcifications. The mass did not show marked enhancement at administration of paramagnetic contrast material, but it sustained its faint moderate inhomogeneous enhancement pattern to include the final phase of the postcontrast examination (Fig 3).
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Figure 2. Transverse fat-suppressed spin-echo T2-weighted MR image of the abdomen (repetition time msec/echo time msec, 1600/70). The signal intensity of the tumor (arrows) is similar to that of the soft-tissue, without necrosis.
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Figure 3a. Transverse breath-hold fat-suppressed T1-weighted gradient-echo MR images (140/6) obtained (a) before administration of intravenous paramagnetic contrast material and at the (b) early and (c) late phases after administration of contrast material. The tumor (arrows) is of intermediate signal intensity on a, faintly and inhomogeneously enhanced with contrast material administration (b), and retains contrast enhancement, without prominent washout (c). The central high-attenuation areas on CT images appear hypointense (arrowhead), which indicates calcification.
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Figure 3b. Transverse breath-hold fat-suppressed T1-weighted gradient-echo MR images (140/6) obtained (a) before administration of intravenous paramagnetic contrast material and at the (b) early and (c) late phases after administration of contrast material. The tumor (arrows) is of intermediate signal intensity on a, faintly and inhomogeneously enhanced with contrast material administration (b), and retains contrast enhancement, without prominent washout (c). The central high-attenuation areas on CT images appear hypointense (arrowhead), which indicates calcification.
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Figure 3c. Transverse breath-hold fat-suppressed T1-weighted gradient-echo MR images (140/6) obtained (a) before administration of intravenous paramagnetic contrast material and at the (b) early and (c) late phases after administration of contrast material. The tumor (arrows) is of intermediate signal intensity on a, faintly and inhomogeneously enhanced with contrast material administration (b), and retains contrast enhancement, without prominent washout (c). The central high-attenuation areas on CT images appear hypointense (arrowhead), which indicates calcification.
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DISCUSSION
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The patient underwent surgery, and the tumor was found to be unresectable since it was fixed to the adjacent structures, and only partial excision was possible. Histopathologic examination of the excised biopsy material revealed densely packed malignant osteoid tissue with calcifications and ossifications, and retroperitoneal extraskeletal osteosarcoma was diagnosed. The tumor was located in the right renal area of this patient, who had a history of right-sided simple nephrectomy.
An initial difficulty in the analysis of this case is determining the tissue from which the mass originated. An adrenal origin should be considered because the nephrectomy was simple and the adrenal gland was conserved. Another consideration should be a soft-tissue mass of retroperitoneal origin, which includes a broad spectrum of abnormal entities (1–6). A large mass arising from a small organ results in disappearance of the organ; this phenomenon is known as the "phantom organ sign" (6). False-positive results of this sign exist, as in the case of huge retroperitoneal masses involving the adrenal gland (6). Thus, it is difficult to exclude adrenal tumors in this case, considering the location of the mass is the only basis for diagnosis.
Adrenal masses can be divided into two physiologic categories on the basis of whether they hypersecrete a hormone (7). Hyperfunctioning adrenal masses, such as pheochromocytomas, aldosteronomas, and cortisol- or androgen-producing tumors, could be excluded in this case, since the clinical history did not include any hormonal imbalance. Nonfunctioning adrenal tumors that may attain great size and show calcification, such as the mass in this case, are adrenal metastasis and carcinoma of the adrenal gland. Both adrenal metastasis and carcinoma typically have a heterogeneous appearance and show marked contrast enhancement on CT and MR images (7). Imaging findings in this case were inconsistent with these features, which might be helpful for exclusion of adrenal carcinoma and metastasis.
Soft-tissue masses of the extraperitoneal spaces are nonspecific, with considerable overlap among the findings (1–6). However, the presence of certain histologic elements having characteristic radiologic appearances on MR images, such as myxoid stroma, fat, collagen fibers, and calcification, have been proposed as being helpful in narrowing the differential diagnosis (1,5,6). The central high-attenuation areas of the mass on CT images are hypointense on MR images; thus, they are consistent with intensely calcified areas. The tumor is moderately inhomogeneous apart from these areas, without any signal that may be compatible with fat, myxoid tissue, necrosis, or hemorrhage.
A retroperitoneal mass with calcification has a wide range of differential diagnoses, including several benign and malignant conditions. The nontumoral benign conditions are exuberant fracture callus, posttraumatic calcified hematoma, and myositis ossificans (8–11). Since the patient had a history of surgery in that area, a foreign body granuloma also should be considered in the differential diagnosis. Foreign body granulomas or encapsulated textilomas (gossypibomas) occur secondary to retained surgical materials, such as sponges, gauzes, or towels, in the area of the procedure and have various clinical and radiologic presentations (12,13). They may have a confusing appearance, such as a heterogeneous mass masquerading as a tumor, with variable contrast enhancement depending on the inflammatory reaction. Calcification of textilomas is not an expected finding, but it has been reported to occur (12). The calcification in the previously reported textiloma case had a peripheral curvilinear pattern, unlike the appearance in our patient.
The benign neoplasms of the retroperitoneum that may calcify include ganglioneuroma, Schwannoma, paraganglioma, hemangioma, and mature teratoma that may be adrenal or extraadrenal in location (1,14). Tumors of neural origin are commonly heterogeneous, with very hyperintense areas on T2-weighted images owing to the myxoid stroma, and the contrast enhancement is marked. Hemangiomas appear hyperintense on T2-weighted images, and the calcifications in hemangiomas appear as phleboliths. Mature teratomas typically have an inhomogeneous internal structure containing fluid, fat, and/or sebum in the form of fat-fluid levels (15,16). These findings did not exist in the present case. Moreover, the invasive behavior of the mass in this patient favored the exclusion of benign processes.
The malignant retroperitoneal tumors that may undergo calcification or ossification are malignant fibrous histiocytoma (termed undifferentiated pleomorphic sarcoma in the current nomenclature), dedifferentiated liposarcoma, malignant mesenchymoma, malignant teratoma, and extraskeletal osteosarcoma (1–3,17–19). Undifferentiated pleomorphic sarcoma, formerly termed malignant fibrous histiocytoma, is seen as a heterogeneous mass having additional myxoid stroma and/or collagen fibers. Dedifferentiated liposarcoma may include bulky calcification areas in some part of the tumor; however, it tends to be more heterogeneous than the mass in this case. It includes more than one type of tissue, which may be fat or myxoid tissue containing necrosis and hemorrhage (3). Malignant mesenchymoma, by definition, typically has two or more malignant fibrosarcomatous components that are expected to be heterogeneous in nature (2,3,19–21). MR imaging displays basically hypointense signal on T1-weighted images and hyperintense signal on T2-weighted images (16). Malignant teratoma occurs in young individuals as a heterogeneous tumor with variable differentiation of germ cells, and it may show calcification. Retroperitoneal extraskeletal osteosarcoma has a variable amount of mineralization, but the calcification is commonly intense and amorphous (3,8–11,20,21). The nonmineralized areas have an attenuation consistent with that of muscle on CT scans and nonspecific intermediate signal intensity on T1-weighted MR images, as in this case. After administration of contrast material, osteosarcomas have variable contrast enhancement. They are commonly hypervascular; however, hypovascular tumors have also been reported (9). Hypovascularity of the malignant osteoid can explain the faint enhancement of the tumor after administration of contrast material in this case.
Extraskeletal osteosarcoma is a rare tumor constituting 4% of osteosarcomas and 1.2% of all soft-tissue sarcomas (10,11). The most common locations of extraskeletal osteosarcomas are the lower extremities (47%), upper extremities (20%), and retroperitoneum (17%). In contrast to osterosarcoma of bone, extraskeletal osteosarcomas occur in older individuals, commonly in the 4th–6th decades of life. Symptoms often include a slowly growing painful mass that is mostly firm at palpation (3). The elevation of alkaline phosphatase levels is a common finding and accepted as a prognostic tumor marker in osteosarcomas (22). High levels of alkaline phosphatase have also been reported in extraskeletal retroperitoneal osteosarcomas (8,9); however, this is not an expected finding in other retroperitoneal tumors. Thus, the firm nature of the tumor at palpation, elevated serum alkaline phosphatase level, and imaging findings should have led to the most likely diagnosis of retroperitoneal extraskeletal osteosarcoma.
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FOOTNOTES
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| Part one of this case appeared 4 months previously and may contain larger images.
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References
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- Nishimura H, Zhang Y, Ohkuma K, Uchida M, Hayabuchi N, Sun S. MR imaging of soft-tissue masses of the extraperitoneal spaces. RadioGraphics 2001;21:1141–1154.[Abstract/Free Full Text]
- Enzinger FM, Weiss SW. Soft tissue tumors. 3rd ed. St Louis, Mo: Mosby–Year Book, 1995.
- Fletcher CDM, Unni KK, Mertens F, eds. World Health Organization classification of tumors: pathology and genetics of tumors of soft tissue and bone. Lyon, France: IARC, 2002.
- Kransdorf MJ. Benign soft-tissue tumors in a large referral population: distribution of specific diagnoses by age, sex, and location. AJR Am J Roentgenol 1995;164:395–402.[Abstract/Free Full Text]
- Kransdorf MJ. Malignant soft-tissue tumors in a large referral population: distribution of specific diagnoses by age, sex, and location. AJR Am J Roentgenol 1995;164:129–134.[Abstract/Free Full Text]
- Nishino M, Hayakawa K, Minami M, Yamamoto A, Ueda H, Takasu K. Primary retroperitoneal neoplasms: CT and MR imaging findings with anatomic and pathologic diagnostic clues. RadioGraphics 2003;23:45–57.[Abstract/Free Full Text]
- Mayo-Smith WW, Boland GW, Noto RB, Lee MJ. State-of-the-art adrenal imaging. RadioGraphics 2001;21:995–1012.[Abstract/Free Full Text]
- van Rijswijk CS, Lieng JG, Kroon HM, Hogendoorn PC. Retroperitoneal extraskeletal osteosarcoma. J Clin Pathol 2001;54:77–78.[Free Full Text]
- Wesseling FJ, Tjon A, Tham RT, Breed W, Klinkhamer PJ. Retroperitoneal extraskeletal osteosarcoma. AJR Am J Roentgenol 1990;155:1139–1140.[Medline]
- Chung EB, Enzinger FM. Extraskeletal osteosarcoma. Cancer 1987;60:1132–1142.[CrossRef][Medline]
- Bane BL, Evans HL, Ro JY, et al. Extraskeletal osteosarcoma: a clinicopathological review of 26 cases. Cancer 1990;65:2762–2770.[CrossRef][Medline]
- Bellin M, Hornoy B, Richard F, et al. Perirenal textiloma: MR and serial CT appearance. Eur Radiol 1998;8:57–59.[CrossRef][Medline]
- Grieten M, Van Poppel H, Baert L, Baert AL, Oyen R. Renal pseudotumor due to a retained perirenal sponge: CT features. J Comput Assist Tomogr 1992;16:305–307.[Medline]
- Rha SE, Byun JY, Jung SE, Chun HJ, Lee HG, Lee JM. Neurogenic tumors in the abdomen: tumor types and imaging characteristics. RadioGraphics 2003;23:29–43.[Abstract/Free Full Text]
- Khong PL, Lam KY, Ooi CG, Liu MJ, Metreweli C. Mature teratomas of the adrenal gland: imaging features. Abdom Imaging 2002;27:347–350.[Medline]
- Davidson AJ, Hartman DS, Goldman SM. Mature teratoma of the retroperitoneum: radiologic, pathologic, and clinical correlation. Radiology 1989;172:421–425.[Abstract/Free Full Text]
- Suzuki S, Furui S, Kokubo T, et al. Retroperitoneal malignant mesenchymoma: imaging findings in five cases. Abdom Imaging 1999;24:92–97.[CrossRef][Medline]
- Choi JE, Chung HJ, Yoo WJ, et al. Retroperitoneal malignant mesenchymoma: a case of mesenchymal mixed tumor with osteosarcoma, leiomyosarcoma, liposarcoma and fibrosarcoma. Korean J Radiol 2002;3:264–266.[Medline]
- Fujiyoshi Y, Nishimura H, Irie K, Morimatsu M. A case of retroperitoneal malignant mesenchymoma. Pathol Int 1994;44:803–807.[Medline]
- Humphrey GM, Brown I, Squire BR, Cullinane C, Picton SV. Extraosseous osteogenic sarcoma: a rare pediatric malignancy—case report and review of the literature. J Pediat Surg 1999;34:1025–1028.[CrossRef][Medline]
- Varma DG, Ayala AG, Guo SQ, Moulopoulos LA, Kim EE, Charnsangajev C. MRI of extraskeletal osteosarcoma. J Comput Assist Tomogr 1993;17:414–417.[Medline]
- Narayanan S. Alkaline phosphatase as tumor marker. Ann Clin Lab Sci 1983;13:133–136.[Abstract]
Congratulations to the 21 individuals who submitted the most likely diagnosis (retroperitoneal extraskeletal osteosarcoma) for Diagnosis Please, Case 89. The names and locations of the individuals, as submitted, are as follows:
Individual responses
- Hisashi Abe, Osaka, Japan
- Gholamali Afshang, MD, Tinley Park, Ill
- Albert J. Alter, Madison, Wis
- Dr Juan Ramón Ayuso, Barcelona, Spain
- Thaworn Dendumrongsup, MD, Songkla, Thailand
- Ángeles Franco, Madrid, Spain
- William Gawman, Waterloo, Ontario, Canada
- Mark Goldshein, MD, Andover, Mass
- Alexis Lacout, MD, Paris, France
- Mario Laguna, West Allis, Wis
- David A. Lisle, Brisbane, Australia
- N. B. S. Mani, MD, Nassau, Bahamas
- Waldir H. Maymone, Rio de Janeiro, Brazil
- Tammam Nehme, East Wenatchee, Wash
- Hatice Tuba Sanal, MD, Ankara, Turkey
- Taro Shimono, MD, Osaka, Japan
- Paul Stark, MD, La Jolla, Calif
- Kouichi Sugiyama, Hamamatsu, Japan
- Norio Takahashi, MD, Fukui, Japan
- William C. Torreggiani, Dublin, Ireland
- Kiyoshi Yasui, MD, Izumo, Japan
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HISTORY
IMAGING FINDINGS
