| Abstract|| |
The incidence of extraskeletal osteosarcomas located in the soft tissues without attachment to the bone or periosteum in only 1 percent. The most common location of these tumors is the lower extremity (42-47 percent); especially the thigh followed by the upper extremity (12-1 percent) and the retroperitoneum (8-17 percent). Hence, we report an extremely rare case of extraskeletal retroperitoneal osteosarcoma.
Keywords: Retroperitoneal, Osteosarcomas, Extraskeletal
|How to cite this article:|
Rastogi R, Bhargava S K. Extraskeletal retroperitoneal osteosarcoma-a case report. Indian J Radiol Imaging 2005;15:59-61
|How to cite this URL:|
Rastogi R, Bhargava S K. Extraskeletal retroperitoneal osteosarcoma-a case report. Indian J Radiol Imaging [serial online] 2005 [cited 2019 Sep 21];15:59-61. Available from: http://www.ijri.org/text.asp?2005/15/1/59/28746
| Introduction|| |
Extraskeletal osteosarcomas, localized in the retroperitoneal space, are very rare neoplasm. The extraskeletal osteosarcomas are very malignant mesenchymal neoplasms reproducing osseous and cartilaginous tissue disconnected from the skeletal system. From a histological point of view, the extraskeletal osteosarcomas are constituted of osseous and cartilaginous tissue with osteo-fibro-chondroblastic cells: the different representation of three types of cells define the variety of extraskeletal osteosarcomas (osteoblastic, chondroblastic, fibroblastic). Histological and ultrastructural studies had failed to find differences between skeletal and extraskeletal osteosarcomas. The etiology of extraskeletal osteosarcoma is frequently idiopathic but sometimes one might get a history of trauma or irradiation. Diagnosis is generally delayed because symptoms are often absent or uncertain, hence prognosis of these neoplasma is always very poor, and especially in relation to the dimension and the possibility of its radical removal.
| Case Report|| |
A 45 years old female patient presented to our hospital with complaints of heaviness associated with a painless mass in the left hypochondrium and lumbar region for 6-8 months. No history of trauma, anticoagulant therapy, radiotherapy and other significant medical condition could be elicited. On examination, a hard mass measuring approximately 15x10 cms was palpable in the left lumbar region extending into the left hypochondrium. No other significant signs and symptoms were noted.
Laboratory investigations were within normal limits except for the raised ESR. An ultrasound examination of the abdomen revealed a hypoechoic ill defined mass with a dense acoustic shadowing in the retroperitoneal region on the left side with anteromedial displacement of the left kidney. The capsule of the left kidney appeared irregular so also its posterior cortex with mildly dilated pelvicaliceal system suggesting the invasion of the kidney by the mass. No other abnormality was noted in the abdomen [Figure - 2].
Scout film of the KUB region revealed a large ill-defined calcified lesion in the region of left kidney. IVP study of the patient revealed a left paravertebral mass with anteromedial displacement of a mildly hydronephrotic left kidney [Figure - 1]. Radiograph of the chest was unremarkable.
Contrast enhanced helical computed tomography (CT) of the abdomen identified a large, in-homogeneous soft tissue mass in the left side of the retroperitoneum. The tumor measured 9.5 x 11 x 7 cm. The posterosuperior part of the mass was predominantly mineralized [Figure - 3]; the inferomedial part showed a large soft tissue mass with low density in the center suggestive of necrosis or hemorrhage. The radiological features suggested an osseous, rather than chondroid nature because of the poorly defined and homogeneous aspect of the mineralisation. The anterior border of the mass was in close proximity to the adjacent left kidney, which was displaced anteromedially [Figure - 4]. The tumor definitely did not arise from adjacent osseous structures and the tumor compressed the psoas muscle. Based on the clinical history and radiographic findings, the diagnosis of an extraskeletal retroperitoneal osteosarcoma was suggested.
An ultrasound guided FNAC and biopsy of the mass revealed histological evidence of malignant osteoid formation. Thus a diagnosis of extraskeletal retroperitoneal osteosarcoma was made.
| Discussion|| |
Extraskeletal osteosarcoma is a rare tumor, constituting approximately 1% of all soft tissue sarcomas and approximately 4% of all osteosarcomas .
Although primary osteosarcomas of bone occur predominantly in the first decades of life, extraskeletal osteosarcomas are rarely encountered under 40 years of age. The pathogenesis of the tumor is unclear; the tumor may occur and be induced at sites that have received previous radiotherapy. In addition, a history of trauma has been reported in 12-30% of patients. There are cases described in which extraskeletal osteosarcoma is presumed to be preceded by myositis ossificans lesions ,,. Few reports of extraskeletal osteosarcoma have detailed radiological findings of this rare neoplasm ,. The imaging techniques showed a large soft tissue tumor, for a large part demonstrating ossification, located in the retroperitoneum.
Another primary osteosarcoma of bone was not found elsewhere in the body. The radiological differential diagnosis of extraskeletal osteosarcoma includes benign and malignant lesions that show mineralisation. The most important benign lesions are calcified hematoma and myositis ossificans. Several mesenchymal tumors can show reactive or metaplastic bone formation - for example, synovial sarcoma, epithelioid sarcoma, liposarcoma, and malignant peripheral nerve sheath tumor .
Both possible benigh lesions could be ruled out. The first because the patient definitely denied previous trauma. Furthermore, the patient did not use anticoagulant medication and the aorta was normal on all studies. Myositis ossificans was unlikely because there was no previous trauma and because of the large size of the lesion. Most myositis ossificans lesions measure 3 - 6 cm in diameter . Moreover, this lesion demonstrated ossification throughout a large part of the tumor and not at the periphery as is seen in myositis ossificans. Furthermore, the adjacent muscles were normal. Differentiating our patient's tumor from other malignant retroperitoneal sarcomas that can show bone formation is more difficult and a biopsy is mandatory for a definitive diagnosis. These tumors are usually large at diagnosis and the symptomatology is short and uncharacteristic. There is no characteristic set of laboratory or roentgenologic findings : some may have elevation of alkaline phosphatase, and majority shows calcification .
Chung EB and Enzinger FM  conducted a retrospective study of 88 cases of extraskeletal osteosarcoma. The study revealed that this tumor affects adults almost exclusively, with a high incidence in patients older than 50 years, and is slightly more common in males (58%) than in female patients. The tumor occurred principally as a soft tissue mass in extremity, with a predilection for the thighs (lower extremity, 46.6%; upper extremity, 20.5%) and the retroperitoneum (17%). Most were deep- seated and were firmly attached to the fascia, but occasionally they were freely movable and confined to the subcutis or dermis. Nearly all presented as an insidiously growing mass rarely causing pain or tenderness. The preoperative duration of symptoms ranged from 2 weeks to 25 years (median, 6 months). A history of prior trauma to the site of the tumor was stated in 12.5% and of radiation in five cases 5.7%.
Microscopically, the tumors contained varying amounts of neoplastic osteoid and bone, sometimes together with islands of malignant-appearing cartilage. Like osteosarcoma of bone, extraskeletal osteosarcoma showed a striking variation in histologic appearance and focally resembled malignant fibrous histiocytoma, fibrosarcoma and malignant schwannoma. Vulpio et al  has reviewed literature on extraskeletal retroperitoneal osteosarcomas and noted that extraskeletal osteosarcomas localized in the retroperitoneal space, are very rare neoplasms.
A case similar to that of ours was reported by Kasahara Y et al . They wrote that among the extraosseous osteogenic sarcoma arising from the somatic soft tissue, involvement of the retroperitoneum is rare. Only 12 cases including theirs have been reported as being of retroperitoneal origin.
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S K Bhargava
E-3, GTB Hospital Complex, Dilshad Garden, New Delhi
Source of Support: None, Conflict of Interest: None
[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4]