Year : 2005 | Volume
: 15 | Issue : 1 | Page : 63--66
Extraosseous osteogenic sarcoma of forearm
A Krishnan, CJ Bhatt, S Lagvankar, PR Patel
Sheth K.M. School of PG Medicine & Research, Smt. N.H.L Municipal Medical College, Sheth V.S. Medical Research Foundation, Ahmedabad - 380006, India
780/1, Jagruti Park Society, Sector-30, Gandhinagar-382030
|How to cite this article:|
Krishnan A, Bhatt C J, Lagvankar S, Patel P R. Extraosseous osteogenic sarcoma of forearm.Indian J Radiol Imaging 2005;15:63-66
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Krishnan A, Bhatt C J, Lagvankar S, Patel P R. Extraosseous osteogenic sarcoma of forearm. Indian J Radiol Imaging [serial online] 2005 [cited 2019 Nov 19 ];15:63-66
Available from: http://www.ijri.org/text.asp?2005/15/1/63/28747
Bone formation or calcification is relatively common in reactive, degenerative processes or neoplasia of the somatic soft tissue. But extraosseous osteogenic sarcoma is exceedingly rare and seldom encountered [1,2]. It is very difficult to diagnose on clinical and radiological grounds. The histopathological characteristics of the tumor have been alluded to and these criteria must be strictly adhered to in diagnosis of extraosseous osteogenic sarcoma. In view of the grave prognosis and because the majority of the extraosseous osteogenic sarcomas infiltrate the surrounding tissue far beyond their palpable border, aggressive surgical approach is recommended by most of the reporters ,,,. Though, with the advent of chemotherapy salvage is practical. Here, we present a patient of extraosseous osteogenic sarcoma of forearm.
Materials and methods (case report)
A 15 year old girl was first seen at our institute in September 1999, with a large painless swelling in the forearm. The patient had first noticed a small swelling of the size of a walnut on the dorsum of middle third forearm six months back.There was no antecedant history of trauma.The swelling did not increase in size substantially .An incisional biopsy was performed in June 1999 which was then reported to be myositis ossificans. The lesion recurred after one month and enlarged in size fairly rapidly over next two months duration. On examination, the swelling was biglobular of the size of eight cm x five cm x four cm, located in mid left forearm on dorso-medial aspect [Figure 1].
The overlying skin was shiny, hypervascular, without oedema and with healed scar of previous operation.It was non-warm,non-tender,non-pulsatile and firm in consistency.The mass was adhered to the underlying muscles of dorsal compartment but not to the bone. There were no affection of distal neurovascular supply. Regional lymph nodes were unremarkable.
Haemogram of the patient including alkaline phosphatase was within normal limits. Plain radiograph of forearm showed soft tissue mass lesion without any calcification
[Figure 2] a,b. Plain CT scan showed a well defined hypodense mass lesion in the posterior compartment of middle forearm [Figure 3] with patchy inhomogenous enhancement on post contrast study.The lesion appears separate with no evidence of erosion of the bone [Figure 4].Adjacent fat planes were partially obliterated and there was no evidence of calcification. It did not reveal any extensive vascularity or infiltration or compression of vessels.The isotope scan of whole body scan was normal.
The tumor was surgically excised with wide margins of 5-6 cm. of skin, muscle and periosteum of ulna without an attempt to dissect the tumor perse. The area was covered with a split thickness skin graft from thigh. Grossly, the specimen contained a well circumscribed mass of the size of 10cm x six cm x five cm.The cut surface was white,firm and homogenous. Microscopically,there was a thin pseudocapsule of compressed connective tissue at some places.Highly pleomorphic, spindle shaped cells, variable in size with eosinophilic cytoplasm and prominent nucleoli were arranged in irregular fashion.Many giant cells of variable size and shape were present.Stroma showed hyalinised cartilaginous matrix with osteoid.Areas of haemorrhage were present with many illformed blood vessels. Fibrous septa were seen forming nodules of tumor tissue.The skin was involved and there was no evidence of periosteal involvement. The post operative course was uneventfull. After 21 days patient was subjected to six cycles of chemotherapy with Cisplatin and Adriamycin at 21 days intervals.The patient was then followed up every three months.There was no evidence of recurrence at four years follow up [Figure 5] a,b [Figure 6].
The first recorded patient of osseous tumor of soft parts located at a distance from the skeleton, was reported by Boneti in 1700, who described an osteoma of the mammary gland . Allan and Soule reported 96 patients review, 26 were from their Mayo's clinic and rest of the patients were a literature review including 46 patients by Fine and Stout (1956) and 9 by Das Gupta et al (1968) rest being individual patients. Further additions have taken place since then and William B. Miller Jr. et al has reported the only forearm extraosseous osteogenic sarcoma .
A soft tumor may be diagnosed as primary extraosseous osteogenic tumor based on three criteria :
1) The presence of uniform morphological pattern of sarcomatous tissues that excludes the possibility of mixed malignant mesenchymal tumor;
2) The production by sarcomatous tissue of malignant osteoid or bone (or both) and
3) The ready exclusion of osseous orgin .
This tumor more commonly affects limb and limb girdles and with a greater preponderance to thigh. A few patient of trunk affection has been reported .Those osteogenic sarcomas that are arising in breast, liver,kidney or other organs are mostly considered to represent malignant teratoma with the gradual pre-eminence of osteogenic tissue and obliteration of all other elements . The tumor affects more commonly the males.
The average age has been 44.5 years .But in our patient it is second decade like primary osteogenic sarcoma. Currently there are three postulated theories of orgin of these tumors.
1) The theory of metaplasia: Under certain environmental conditions, connective tissue can revert back to its embroyonic state and then redifferentiate in aberrant directions to produce cartilage, osteoid tissue, and bone.
2) The theory of embroyonic rests: Misplaced osteogenic cells during development may remain dormant for many years and then begin to grow and produce bone due to a change in physiological conditions at the unnatural site.
3) Theory of transport of osteoblast : Metastasis of osteoblasts by blood stream can lead to their deposition in unusual location where they produce bone and may transform to take a malignant form ,,. Trauma as a causative factor was not noted in any of the reported series though it may have drawn the attention to a pre-existing lesion.Malignant degeneration of a precursor benign lesion,myositis ossificans,has been documented  but the history would be very long standing.In our patient's biopsy we could not identify any tissue suggestive of non malignant lesion, but it is possible that the tumor grew to such a size that it destroyed its precursor. Gross pathologic characteristics are variable. The tough pseudo capsule is adherent to surrounding tissue.
Consistency varies from liquefying softness to bony hardness. The size varies from 1.5 to 20 cm. The cut surface of the tumor varies between red and grey, greyish white, whitish grey or yellowish white; often several combinations. Areas of haemorrhage and necrosis are frequent. Central part is usually cystic and periphery is firm and rarely palpable specks of calcification can be seen ,. Microscopically, striking histological feature is the nodular arrangement of the tumor, highly cellular, containing both spindle and giant cells and frequently arranged in cords. The degree of cellular pleomorphism and number and type of giant cells varies but there is cellular uniformity throughout the tumor. Like the basic osteogenic sarcoma it can be osteoblastic, or chondroblastic, or fibroblastic ,.
Metastasis, local, regional and systemic accounts for the very high frequency of recurrences and grave prognosis ,. Haemogram is only corroboratory. Increased alkaline phosphatase is valuable in osteoblastic type and for monitoring response to treatment and detecting recurrence . Plain radiography usually shows soft tissue shadow and in a few cases calcification. Bones are usually normal except in late direct extension from the primary tumor .Angiography would show a hypervascular soft tissue mass with all the angiographic characteristics of a malignant lesion .
CT scan would further help in excluding the osseous origin . It emphasizes the osseous content of the lesion ,. MRI images have a low density signal on T-1 and a bright signal on T-2. MRI is the best technique for accurately determining the extent of extraosseous osteosarcoma . Differential diagnosis must include benign osseous tumor of soft tissues, mixed mesenchymal sarcomas, parosteal osteogenic sarcomas and atypical forms of myositis ossificans,. Allan and Soule compared the effects of local resection, wide local resection with irradiation,secondary amputation for recurrence and primary amputation and found no obvious difference in survival.In view of the grave prognosis of the high grade malignant tumor surgeon must remove the whole of the tumor with wide zone of uninvolved tissue,.
Recurrences are very common and to avoid local recurrences and multiple inadequate excisions, it is suggested that adequate biopsy diagnosis of the primary lesion be made at the onset, following which wide excision be performed. Since most tumors occur in extremities, theoretically ideal treatment to improve survival rates is major amputation,,,. With radiation therapy only short term palliation is achieved.Chemotherapy is indicated as a preoperative neoadjuvant to facilitate limb salvaging, local control and postoperatively to minimize the risk of pulmonary metastasis.
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