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  Table of Contents    
CASE REPORT  
Year : 2022  |  Volume : 65  |  Issue : 2  |  Page : 452-454
Soft tissue aneurysmal bone cyst of left hemithorax: An extremely rare case


1 Department of Oncopathology, The Gujarat Cancer and Research Institute, New Civil Hospital Campus, Asarwa, Ahmedabad, Gujarat, India
2 Department of Surgical Oncology, The Gujarat Cancer and Research Institute, New Civil Hospital Campus, Asarwa, Ahmedabad, Gujarat, India

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Date of Submission12-Sep-2020
Date of Decision05-Feb-2021
Date of Acceptance26-May-2021
Date of Web Publication14-Apr-2022
 

   Abstract 


Aneurysmal bone cyst (ABC) is a benign expansile cystic lesion that can affect any bone of the skeleton, especially the femur, tibia, and humerus. Lesions with histologic features of an ABC can be originated within soft tissue in exceedingly rare cases. Extra-skeletal ABC may mimic a variety of benign and malignant lesions and can be confused with other common or rare giant cell-rich tumors of soft tissue. Clinical, radiological and histologic correlation are crucial in reaching the correct diagnosis. Here we report a case of an extra-skeletal ABC arising in left hemithorax in a 13-year-old girl and discuss the common differential diagnosis of this rare entity.

Keywords: Aneurysmal bone cyst, extra-skeletal, hemithorax, soft-tissue

How to cite this article:
Patra S, Trivedi P, Kaur K, Sunitha S, Sharma MR. Soft tissue aneurysmal bone cyst of left hemithorax: An extremely rare case. Indian J Pathol Microbiol 2022;65:452-4

How to cite this URL:
Patra S, Trivedi P, Kaur K, Sunitha S, Sharma MR. Soft tissue aneurysmal bone cyst of left hemithorax: An extremely rare case. Indian J Pathol Microbiol [serial online] 2022 [cited 2022 Dec 3];65:452-4. Available from: https://www.ijpmonline.org/text.asp?2022/65/2/452/343163





   Introduction Top


Aneurysmal bone cyst (ABC), a benign tumor of bone, most frequently arises from the metaphyses of long bones and the posterior elements of vertebral bodies.[1] It generally occurs during the first two decades of life and has no sex predilection.[1] Radiologically, ABC is usually eccentric, lytic, and expansile having well-defined margins. Histologically, it is composed of blood-filled cystic spaces separated by fibrous septa that contain an admixture of fibroblasts, variable numbers of osteoclast-type giant cells, and reactive woven bone. Areas resembling ABC can be found in other benign and malignant bone tumors.[1] ABC developing in soft tissue is extremely rare, and very few cases have been reported in the literature.[2],[3],[4] Here, we describe the clinicopathologic findings of an additional case.


   Case Presentation Top


A 13-year-old girl presented with difficulty in breathing and pain in the left side of the chest for the last 1 month. On imaging (computed tomography, CT), a 16 cm × 12 cm × 12 cm sized heterogeneously enhancing soft tissue density mass was noted involving the left hemithorax [Figure 1]a, compressing the posterior aspect of the fourth rib and underlying lung. Splaying of other ribs was noted without bone destruction. The mass abutted the lateral chest wall. It showed internal cystic areas and peripheral calcification. Minimal amount of pleural effusion was also evident. Radiologically possibility of ABC arising from a rib was considered. Magnetic resonance imaging (MRI) was not done.
Figure 1: (a) Contrast-enhanced CT scan in sagittal plane shows a solid and cystic mass in the left hemithorax (yellow arrows: the entire lesion; arrowhead: calcification within the lesion); CT: computed tomography. (b) Gross appearance: Cut surface of the mass showing gray-white to a tan-brown solid area with hemorrhagic spaces

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A CT-guided core biopsy was done. Histopathological examination revealed bland spindle cell proliferation and multinucleated osteoclast-type giant cells on hyalinized stroma. So, a diagnosis of a benign spindle cell lesion with osteoclast-type giant cells was offered.

Left thoracotomy was done. Intraoperatively, the mass was seen completely separate from the posterior surface of ribs or any other bony attachment and compressed the surrounding lung tissue. The mass was excised in toto. Grossly, it was well-circumscribed and encapsulated. The size of the mass was 15 cm × 13 cm × 12 cm. Cut surface showed multiple blood-filled cystic spaces, tan-brown solid areas, pearly white cartilaginous and peripheral bony areas [Figure 1]b. Multiple sections (16 in number) were submitted from different areas. Histopathology showed blood-filled cystic cavities with intervening fibrous septa containing multinucleated osteoclast-type giant cells, bland fibroblastic cell proliferation on hyalinized stroma, calcification, woven bone, and focal hyaline cartilage. Cystic cavities were lined by osteoclast-type giant cells at places. Deposition of “blue bone ” was also evident [Figure 2]a, [Figure 2]b, [Figure 2]c, [Figure 2]d. Lamellar bone formation was also noted. The interface between the lamellar bone and tumor showed complete infarct-type necrosis. The histomorphology was suggestive of ABC. Hence, in view of clinical and radiological features, the final diagnosis was rendered as an ABC of soft tissue. The patient had no recurrence in the 1-year follow-up period.
Figure 2: Microscopic findings (a) Blood-filled cystic cavities with intervening fibrous septa (H&E, 20X); (b and c) Intervening septa show proliferation of bland fibroblasts with intermingled osteoclast-type giant cells (H&E, 40X); (d) Interface between the tumor and deposition of the so-called “ blue bone ” (H&E, 10X); H&E: Hematoxylin and eosin

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   Discussion Top


The first case of soft tissue ABC was reported by Salm and Sissons in 1972. They described two cases that according to their illustrations, exhibited microscopic features of soft tissue ABC, resembling intraosseous ABC, and they categorized them as “vascular cystic tumors of soft tissue. ”[5] Since then, approximately 36 cases have been described in the literature till now including the recently studied six cases.[4]

It has been controversial as to whether ABC is neoplastic or reactive. Now, it is generally accepted that primary ABC is a neoplastic process owing to rearrangements involving the ubiquitin-specific peptidase 6 (USP6) gene located at chromosome 17p13.2. The most common translocation is t(16;17) (q22; p13).[6] The tumor can be locally aggressive with the destruction of the affected bone and impingement on surrounding tissues. ABC may also occur secondarily to other benign or malignant bone tumors. The secondary ABC does not harbor a USP6 gene rearrangement, and thus, is thought to be reactive.[1] However, the USP6 gene rearrangement study was not done for the present case.

Recognizing a soft tissue lesion as an ABC, however, remains a significant diagnostic challenge for both the radiologist and pathologist, given its rarity and similarity to other lesions. Imaging features of soft tissue ABC may be solid, solid-cystic, or multi-cystic with peripheral rim of thin or coarse mineralization. Fluid-fluid levels, septal enhancement, or perilesional edema are typical findings in MRI. The entities closely resembling soft tissue ABC radiologically are myositis ossificans, ossifying fibromyxoid tumor, giant cell tumor of soft tissue, liquified hematoma, and cavernous hemangioma. The presence of thin rim of mineralization, septations, fluid-fluid levels, and cavities help to distinguish from other mimics.[4] The histologic diagnosis of ABC in needle core biopsies may be very difficult as the differential diagnoses include virtually all giant cell-rich lesions, such as giant cell tumor of soft tissue, myositis ossificans, nodular fasciitis with osteoclastic giant cells, brown tumor of hyperparathyroidism, and extra-skeletal telangiectatic osteosarcoma. Chondromesenchymal hamartoma of the chest wall, a rare entity, is a close differential diagnosis particularly when the soft tissue ABC arises in the vicinity of a rib in the thoracic cavity as in our case.

Morphologically, myositis ossificans is solid and characterized by a pattern of zonation. The mesenchymal spindle cells at the central portion merge peripherally with plump cells admixed with poorly formed osteoid production, that changes into mature bone at the interface with the surrounding skeletal muscle. This morphologic pattern is not seen in soft tissue ABC. Nodular fasciitis often contains scattered osteoclast-type giant cells. Indeed, the diagnosis of nodular fasciitis was initially made in one of the published cases of soft tissue ABC.[7] However, the prominent cystic change and the peripheral rim of bone formation, typical of ABC, are not found in Nodular fasciitis (NF). Soft tissue giant cell tumor can be confused with soft tissue ABC because of the presence of osteoclast-type giant cells in both lesions. Soft tissue giant cell tumor may undergo cystic degeneration but, the cysts are not as prominent as in soft tissue ABC, and the solid areas showing the classic features of giant cell tumor are invariably absent in ABC.[8],[9] Extra-skeletal telangiectatic osteosarcomas, which are very rare, have similar gross features to those of soft tissue ABC. However, the septa contain cells with obvious features of malignancy which are not seen in soft tissue ABC. Chondromesenchymal hamartoma of the chest wall is a benign primary bone tumor arising from the rib and shows blood-filled ABC-like spaces, bland fibroblastic proliferation, multinucleated osteoclast-type giant cells, hyaline cartilage, and woven bone formation.[10] Soft tissue ABC can be misdiagnosed as chondromesenchymal hamartoma of the chest wall, especially when it arises in close vicinity of a rib causing much compression and even erosion on the posterior or lateral surface of the rib. In this setting, the determination of the site of origin of the lesion by radiology is extremely helpful to avoid potential misdiagnosis.

For soft tissue ABCs, the treatment of choice is wide local excision. Local recurrence is uncommon. Only 5% of the reported cases in the literature recurred after incomplete surgical excision.[4],[5],[6]

In summary, soft tissue ABC is an extremely rare benign tumor that is histologically indistinguishable from an ABC arising from the bone. Morphologically, it can be confused with a variety of giant cell-rich reactive and neoplastic processes. Surgical excision is the treatment of choice. Recurrence is highly unlikely after complete excision.

Acknowledgment

We acknowledge all the technical staffs of histopathology section in our department for their support.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

1.
Agaram NP, Bredella MA. Aneurysmal bone cyst. In: WHO Classification of Soft Tissue and Bone Tumours. Lyon: IARC; 2020.  Back to cited text no. 1
    
2.
Amir G, Mogle P, Sucher E. Case report 729: Myositis ossificans and aneurysmal bone cyst. Skeletal Radiol 1992;21:257-9.  Back to cited text no. 2
    
3.
Nielsen GP, Fletcher CD, Smith MA, Rybak L, Rosenberg AE. Soft tissue aneurysmal bone cyst: A clinicopathologic study of five cases. Am J Surg Pathol 2002;26:64-9.  Back to cited text no. 3
    
4.
Song W, Suurmeijer AJH, Bollen SM, Cleton-Jansen AM, Bovee JVMG, Kroon HM. Soft tissue aneurysmal bone cyst: Six new cases with imaging details, molecular pathology, and review of the literature. Skeletal Radiol 2019;48:1059-67.  Back to cited text no. 4
    
5.
Salm R, Sissons HA. Giant-cell tumours of soft tissues. J Pathol 1972;107:27-39.  Back to cited text no. 5
    
6.
Dal Chin P, Kozakewich HP, Goumnerova L, Mankin HJ, Rosenberg AE, Fletcher JA. Variant translocations involving 16q22 and 17p13 in solid variant and extraosseous forms of aneurysmal bone cyst. Genes Chromosomes Cancer 2000;28:233-4.  Back to cited text no. 6
    
7.
Shannon P, Bedard Y, Bell R, Kandel R. Aneurysmal cyst of soft tissue: Report of a case with serial magnetic resonance imaging and biopsy. Hum Pathol 1997;28:255-7.  Back to cited text no. 7
    
8.
O'Connell JX, Wehrli BM, Nielsen GP, Rosenberg AE. Giant cell tumors of soft tissue: A clinicopathologic study of 18 benign and malignant tumors. Am J Surg Pathol 2000;24:386-95.  Back to cited text no. 8
    
9.
Oliveira AM, Dei Tos AP, Fletcher CD, Nascimento AG. Primary giant cell tumor of soft tissues: A study of 22 cases. Am J Surg Pathol 2000;24:248-56.  Back to cited text no. 9
    
10.
Fritchie KJ, Gambarotti M. Chondromesenchymal hamartoma of chest wall. In: WHO Classification of Soft Tissue and Bone Tumours. Lyon: IARC; 2020.  Back to cited text no. 10
    

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Correspondence Address:
Priti Trivedi
Department of Oncopathology, The Gujarat Cancer and Research Institute, New Civil Hospital Campus, Asarwa, Ahmedabad, Gujarat - 380016
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/IJPM.IJPM_1117_20

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