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Year : 2011  |  Volume : 54  |  Issue : 3  |  Page : 616-617
Aneurysmal cyst of soft tissue of the diaphragm presenting as posterior mediastinal mass

1 Department of Pathology, Christian Medical College, Vellore, India
2 Department of Thoracic Surgery, Christian Medical College, Vellore, India
3 Department of Radiology, Christian Medical College, Vellore, India

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Date of Web Publication20-Sep-2011

How to cite this article:
Manipadam MT, Abraham R, Kavunkal AM, Gibikote S, Cherian VK. Aneurysmal cyst of soft tissue of the diaphragm presenting as posterior mediastinal mass. Indian J Pathol Microbiol 2011;54:616-7

How to cite this URL:
Manipadam MT, Abraham R, Kavunkal AM, Gibikote S, Cherian VK. Aneurysmal cyst of soft tissue of the diaphragm presenting as posterior mediastinal mass. Indian J Pathol Microbiol [serial online] 2011 [cited 2022 Aug 16];54:616-7. Available from: https://www.ijpmonline.org/text.asp?2011/54/3/616/85117

Primary aneurysmal cysts of soft tissue (ACST), otherwise known as extraosseous aneurysmal bone cysts, are rare tumors with around 15 cases reported in the English literature so far. ACSTs are identical in gross and microscopic appearance to aneurysmal bone cysts (ABCs) except that they are extraosseous. The present case was attached to the diaphragm, a previously unreported location for ACST.

A 14-year-old girl presented with left-sided chest pain and dyspnea on exertion of five months duration. On examination, there was decreased air entry over left inframammary and infrascapular areas. Chest X-ray showed a homogenous mass lesion in the left middle and lower zones obscuring the left hemi-diaphragm and lower cardiac margin. A post contrast computed tomography (CT) scan of the thorax was then done, which showed a large predominantly cystic, well-defined mass posteriorly in the left hemithorax abutting on the chest wall and contiguous with the diaphragm [Figure 1]a. It had multiple enhancing septations and irregular areas of calcification. The ribs were normal. There was no neural canal widening or extension into the spinal canal. Based on the imaging findings and the age of the child, germ cell tumor was the most likely differential considered. Left posterolateral thoracotomy and excision of the mass was done. The tumor was in the posterior mediastinum occupying the left hemithorax and there was no connection to the adjacent bones radiologically or peroperatively. The tumor was densely adherent to the diaphragm, with feeder vessels from it. The specimen received in the pathology laboratory was an encapsulated soft tissue mass 11 cm Χ 7 cm Χ 4 cm. The cut surface showed a multiloculated cystic tumor with spaces ranging from 0.1 to 2.5 cm filled with blood and serous fluid [Figure 1]b. The septa between the cysts had a fleshy pale grey cut surface. Microscopy showed a typical ABC like picturewith a well circumscribed tumor with multiple blood filled spaces with no definite lining, separated by septa containing bland fibroblasts [Figure 2]a, clumps of osteoid, and woven bone [Figure 2]b, the latter arranged in long curved trabecule, often taking the contours of the cystic spaces. Osteoclast type giant cells were seen lining the spaces and also in small clusters in the septa [Figure 2]b. A peripheral shell of lesional woven bone was present.
Figure 1: (a) Axial computed tomography (CT) section of the thorax (post contrast) showing the large multiseptate, predominantly cystic mass in the left hemithorax. The fluid-fluid levels are faintly visualised in few of the loculations, (b) Cut section of the gross specimen with multiple blood filled cysts

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Figure 2: (a) H and E, x100. Multiple blood filled spaces separated by fibrous sepate with focal aggregates of osteoclast type multi nucleate giant cells, (b) H and E, x200. Trabeculae of woven bone and osteoid surrounding the cystic space. Inset: High power of multi nucleate giant cells

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The term primary aneurysmal cyst of soft tissues was first introduced by Rodriguez Peralto et al., [1] although there have been earlier reports of soft tissue lesions which fitted in exactly with ACST but called by other descriptive names. ACSTs are very rare, the present case being the sixteenth reported in English literature. The age of the patients has ranged from 7 to 57 years. [2] Most of the reported ACSTs have been located in skeletal muscle and soft tissues of extremities, although other sites have been reported [Table 1]. [2],[3],[5] In the present case, the tumor was located in the posterior mediastinum and was seen attached to the diaphragm. The tumor had no connection to the bones or to the great vessels. The classical radiological features of ACST on CT scan include a circumscribed soft tissue mass with a well-defined ring of osseous density around a less dense and septate central area. On magnetic resonance imaging (MRI), ACST appears as a multi loculated fluid filled cyst with peripheral rim of bone. ACSTs are known to have fluid- fluid levels on CT and MRI (which was also seen in our case), and sequential MRI changes from a predominantly solid lesion to a cystic lesion have been reported. [5] Histologically, the ACSTs are exactly similar to their osseous counterparts and are composed of multiple cystic spaces filled with blood and separated by fibrous septa containing osteoclast type multinucleate giant cells and woven bone and osteoid in addition to loosely arranged proliferating fibroblasts. The osteoid and woven bone often takes up the contour of the blood filled cysts. Calcified fibromyxoid matrix with a chondroid aura similar to that described in ABCs, have also been seen in ACSTs. [1] Nielsen et al. describe the presence of spiculated and basophilic bone in one of their five cases. [4] Translocation involving the long and short arms of chromosome 17 have been reported. [4] These and other reports of cytogenetic abnormalities in ACST support the view that these lesions are neoplastic in nature, superseding the earlier theory that ABCs and ACSTs are reparative in nature, probably secondary to trauma. [1] The latter view was considered mainly due to the blood filled spaces, the polymorphic cell population of fibroblasts and osteoclast type multinucleate giant cells and the radiological similarities shared with myositis ossificans.
Table 1: Age and location of some of the previously reported ACSTs

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This is the first case report of ACST presenting in the posterior mediastinum in English medical literature. The tumor was attached to the skeletal muscles of the diaphragm, a previously unreported location.

   Acknowledgment Top

The authors thank Prof. Noel Walter, MD, FRCPath, for confirming the diagnosis.

   References Top

1.Rodriguez- Peralto JL, Lopez-Barea F, Sanchez-Herrera S, Atienza M. Primary aneurysmal cyst of soft tissues (extraosseous aneurysmal cyst). Am J Surg Pathol 1994;18:632-6.  Back to cited text no. 1
2.Salm R, Sissons HA. Giant cell tumors of soft tissues. J Pathol 1972;107:27-39.  Back to cited text no. 2
3.Petrik PK, Findlay JM, Sherlock RA. Aneurysmal cyst, bone type, primary in an artery. Am J Surg Pathol 1993;17:1062-6.  Back to cited text no. 3
4.Nielsen GP, Fletcher CD, Smith MA, Rybak L, Rosenberg AE. Soft tissue Aneurysmal bone cyst. A clinicopathologic study of 5 cases. Am J Surg Pathol 2002;26:64-9.  Back to cited text no. 4
5.Shannon P, Bedard Y, Bell R, Kandel R. Aneurysmal cyst of soft tissue: Report of case with serial magnetic resonance imaging and biopsy. Hum Pathol 1997;28:255-7.  Back to cited text no. 5

Correspondence Address:
Marie Therese Manipadam
Department of General Pathology, ASHA Buildings, Christian Medical College, Vellore - 632 004, Tamil Nadu
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0377-4929.85117

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  [Table 1]


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