|Year : 2014 | Volume
| Issue : 3 | Page : 199-201
Extraosseous aneurysmal bone cyst: A rare presentation
Onteddoo Joji Reddy, Jamkhana Abdul Gafoor, Balla Suresh, Polysetty Obuleswar Prasad
Department of Radiology, Government General Hospital, Bhudhawarapeta, Kurnool, Andhra Pradesh, India
|Date of Web Publication||17-Sep-2014|
Onteddoo Joji Reddy
Department of Radiology, Government General Hospital, Bhudhawarapeta, Kurnool, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
A 55-year-old female developed a gradually increasing soft-tissue mass with peripheral calcifications in the lower thigh. The mass was surgically removed. The lesion was histologically identical to an aneurysmal bone cyst (ABC), therefore, it was diagnosed as an extraosseous ABC. The differential diagnoses and a review of the literature are presented.
Keywords: Aneurysmal bone cyst, extraosseous, myositis ossificans
|How to cite this article:|
Reddy OJ, Gafoor JA, Suresh B, Prasad PO. Extraosseous aneurysmal bone cyst: A rare presentation. J NTR Univ Health Sci 2014;3:199-201
| Introduction|| |
Aneurysmal bone cyst (ABC) is a common benign bone tumor if it arises from bones. But aneurysmal bone cyst arising from soft-tissues is very rare. Histologically aneurysmal cysts of soft-tissue are very similar to ABCs arising from the bone. They are characterized by blood filled spaces separated by connective tissue septa containing fibroblasts, osteoclast-like giant cells, and reactive woven bone.  A search of the English literature found only few case reports of soft-tissue ABC.
| Case report|| |
A 55-yr-old female attended our department with the chief complaints of swelling over lower medial aspect of right thigh since 1 year and was associated with vague pain. On examination, approximately 10 cm × 5 cm mass lesion noted in the lower thigh on the medial aspect, and it was partly mobile. It did not restrict movement of the thigh. X-ray lower thigh showed a well-defined oval shaped mass lesion with peripheral calcified wall and septations were present [Figure 1]. Contrast enhanced computed tomography (CT) showed a well-defined predominantly cystic mass lesion with wall calcification and internal septations filled with fluid [Figure 2]a and b]. Peripheral wall and septations showed moderate enhancement [Figure 2]c]. Magnetic resonance imaging (MRI) (0.3 T) showed heterogenous cystic mass lesion with hypointense wall in all sequences and with internal fluid intensity [Figure 3]a-c]. Based on the imaging findings myositis ossificans and calcified hydatid cyst was considered as differential diagnosis. Excision of the lesion was done. The lesion was located in intermuscular planes in the medial compartment group of muscles and there was no communication with the bone either radiologically or pre-operatively. The cut surface of the specimen showed multi-loculated cystic mass with internal septations filled with blood and serous fluid [Figure 4]. Histopathology showed typical ABC like picture, cystic spaces filled with blood and the wall consists of fibrous tissue, multinucleate giant cells, trabaculae of mature bone, and focal areas showed necrotic bone [Figure 5]a and b].
|Figure 1: X-ray lower thigh showing a well-defi ned oval shaped mass lesion with peripheral calcifi ed wall and septations|
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|Figure 4: The cut surface of the specimen showing multi-loculated cystic mass with internal septations fi lled with blood and serous fl uid|
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| Discussion|| |
Unlike the more common primary bone lesion, soft-tissue ABC is rare. Soft-tissue aneurysmal bone cysts are known to occur in subcutaneous tissues, skeletal muscle and rare sites such as larynx  and arterial walls. 
Radiologically ABCs appear as heterogenous in appearances due to varying amounts of blood, fluid, and fibrous tissue in CT and MRI. In general, ABCs have areas of internal septations with areas of bright signal on T1, T2W and gradient echo images, depending on the chronicity of associated hemorrhage. The radiological differential diagnosis of soft-tissue aneurysmal cysts includes giant cell tumors of soft-tissues, extraskeletal osteogenic sarcoma,  myositis ossificans circumscripta and calcified intramuscular hydatids when they occur in muscles. Myositis ossificans circumscripta and extraosseous ABC share some common etiological, morphological and histopathological characteristics. Unidentified repetitive micro trauma to the soft-tissues may be the predisposing factor for this soft-tissue ABCs and myositis ossificans. Radiographically and histologically myositis ossificans circumscripta shows zonal phenomenon during maturation. This type of zonal phenomenon is not seen in extraosseous ABCs. Definitive diagnosis is made only by histopathological examination. The exact etiology of these soft-tissue ABCs are not clearly known until now. Karkuzhali et al. described neoplastic nature of multiple soft-tissue aneurysmal bone cysts. 
| Conclusion|| |
The case is reported for its rarity and to create awareness of several primary bone lesions, that can arise from soft-tissues exclusively or in combination with underlying bone lesions.
| References|| |
|1.||Leithner A, Machacek F, Haas OA, Lang S, Ritschl P, Radl R, et al. Aneurysmal bone cyst: A hereditary disease? J Pediatr Orthop B 2004;13:214-7. |
|2.||Della Libera D, Redlich G, Bittesini L, Falconieri G. Aneurysmal bone cyst of the larynx presenting with hypoglottic obstruction. Arch Pathol Lab Med 2001;125:673-6. |
|3.||Petrik PK, Findlay JM, Sherlock RA. Aneurysmal cyst, bone type, primary in an artery. Am J Surg Pathol 1993;17:1062-6. |
|4.||Karkuzhali P, Bhattacharyya M, Sumitha P. Multiple soft tissue aneurysmal cysts: An occurrence after resection of primary aneurysmal bone cyst of fibula. Indian J Orthop 2007;41:246-9. |
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]