Benign chondroblastoma with secondary aneurysmal bone cyst in scapula

Introduction Chondroblastoma is a rare benign bone tumour, but locally destructive lesion although metastases may occur. It usually presents in the second decade of life. It is typically localised in the epiphyses of the long bones. Localisation in flat bones is unusual. Males are affected more often than females, the ratio being approximately 2:1. Common clinical symptoms are pain and a decreasing range of motion of adjacent joints. The authors report a case of a 17-year-old female who presented with an expansive osteolytic lesion in the infraspinous part of the left scapula, mimicking aneurysmal bone cyst (ABC). Computed tomographic (CT) scan showed cystic areas, thinning and erosion of the overlying cortex. The biopsy led to the diagnosis of chondroblastoma. Scapula is a rare site for this lesion to develop and to the best of the authors’ knowledge only a few cases have been reported. This tumour is rare in flat bones, and may mimic other benign or malignant lesions. It is, therefore, essential to perform a biopsy in order to obtain a definite diagnosis. We describe a rare case of a large primary scapular chondroblastoma effectively treated with subtotal removal of the scapula, discussing the most prominent radiological and histopathological characteristics. Case report A 17-year-old female was admitted in our institute with complaints of progressive painless swelling of the left scapula for three months. There was no history of trauma or infection, no history of loss of appetite or loss of weight. On physical examination there was a firm, large, mild tender mass located at the infraspinous part of the left scapula. Margins were ill defined and gradually merging with the rest of the scapula. Swelling was mobile along with the scapula. Her shoulder movements were normal. There was no pigmentation or venous dilation on the overlying skin. There is ecchymosis over the swelling due to fine needle aspiration cytology (Figure 1). Plain X-ray showed an expansile, osteolytic lesion in the infraspinous part of the left scapula. Fine needle aspiration cytology showed haemorrhagic fluid with features suggestive of ABC (Figure 2). CT scan showed an expansile, osteolytic lesion of the left scapula involving the body with soft tissue Abstract Introduction Chondroblastoma is a rare benign bone tumour, which presents as a locally destructive lesion, although metastases is not uncommon. It commonly presents in the second decade of life. It is typically localised in the epiphyses of the long bones. Chondroblastoma is a rare benign tumour which is common in long bones. However, there may be unusual presentations such as those in flat bones (scapula). We report a rare case of chondroblastoma in scapula. Case report A 17-year-old female was admitted in our institute with complaints of progressive painless swelling of the left scapula for three months. On physical examination there was a firm, large, mild tender mass located at the infraspinous part of the left scapula. Margins were ill defined and gradually merging with the rest of the scapula. Swelling was mobile along with scapula. Through a posterior scapular approach (Das Gupta’s approach), the tumour was excised enbloc along with marginal resection of scapula below the spinous process. The whole specimen was sent for histopathological examination, which confirmed the diagnosis of chondroblastoma with areas of aneurysmal bone cyst. Postoperative patient recovery was uneventful with complete range of movements. Conclusion Radiographic diagnosis of an atypical chondroblastoma is more difficult


Introduction
Chondroblastoma is a rare benign bone tumour, but locally destructive lesion although metastases may occur.It usually presents in the second decade of life.It is typically localised in the epiphyses of the long bones.Localisation in flat bones is unusual.Males are affected more often than females, the ratio being approximately 2:1.Common clinical symptoms are pain and a decreasing range of motion of adjacent joints.
The authors report a case of a 17-year-old female who presented with an expansive osteolytic lesion in the infraspinous part of the left scapula, mimicking aneurysmal bone cyst (ABC).Computed tomographic (CT) scan showed cystic areas, thinning and erosion of the overlying cortex.The biopsy led to the diagnosis of chondroblastoma.Scapula is a rare site for this lesion to develop and to the best of the authors' knowledge only a few cases have been reported.This tumour is rare in flat bones, and may mimic other benign or malignant lesions.It is, therefore, essential to perform a biopsy in order to obtain a definite diagnosis.
We describe a rare case of a large primary scapular chondroblastoma effectively treated with subtotal removal of the scapula, discussing the most prominent radiological and histopathological characteristics.

Case report
A 17-year-old female was admitted in our institute with complaints of progressive painless swelling of the left scapula for three months.There was no history of trauma or infection, no history of loss of appetite or loss of weight.
On physical examination there was a firm, large, mild tender mass located at the infraspinous part of the left scapula.Margins were ill defined and gradually merging with the rest of the scapula.Swelling was mobile along with the scapula.Her shoulder movements were normal.There was no pigmentation or venous dilation on the overlying skin.There is ecchymosis over the swelling due to fine needle aspiration cytology (Figure 1).Plain X-ray showed an expansile, osteolytic lesion in the infraspinous part of the left scapula.Fine needle aspiration cytology showed haemorrhagic fluid with features suggestive

Introduction
Chondroblastoma is a rare benign bone tumour, which presents as a locally destructive lesion, although metastases is not uncommon.It commonly presents in the second decade of life.It is typically localised in the epiphyses of the long bones.Chondroblastoma is a rare benign tumour which is common in long bones.However, there may be unusual presentations such as those in flat bones (scapula).We report a rare case of chondroblastoma in scapula.

Case report
A 17-year-old female was admitted in our institute with complaints of progressive painless swelling of the left scapula for three months.On physical examination there was a firm, large, mild tender mass located at the infraspinous part of the left scapula.Margins were ill defined and gradually merging with the rest of the scapula.Swelling was mobile along with scapula.Through a posterior scapular approach (Das Gupta's approach), the tumour was excised enbloc along with marginal resection of scapula below the spinous process.The whole specimen was sent for histopathological examination, which confirmed the diagnosis of chondroblastoma with areas of aneurysmal bone cyst.Postoperative patient recovery was uneventful with complete range of movements.components and cystic areas, thinning and erosion of overlying cortex and narrow zone of transition (Figure 3).The lesion measured about 6.1 × 4.2 × 5.5 cm.No evidence of calcification was seen within the lesion.Features were suggestive of ABC or telengiectactic osteosarcoma.

Conclusion Radiographic diagnosis of an atypical chondroblastoma is more difficult
Magnetic resonance imaging (MRI) with contrast showed a complex cystic mass lesion of the left scapula body medial blade infraspinatus location involving the infraspinatus muscle measuring 4.5 × 6.8 × 6.8 cm (Figure 4).There is destruction of scapula extending into the subscalpularis muscles.The lesion showed a soft tissue intensity solid component and cysts showed fluid-fluid level layering, the dependent showed minimal T1 hyperintensity.Multiple thick septation and loculations were noted.Solid components showed moderate post contrast enhancement.Rest of scapula spinous and glenoid process appeared normal.Probable diagnosis was suggestive of ABC, round and spindle cell tumours arising from scapula or infraspinatus muscle.
Through a posterior scapular approach (Das Gupta's approach), the tumour was excised enbloc along with marginal resection of scapula below the spinous process.The whole are round to polygonal, have oval bland nuclei, few show longitudinal grooves with a clear cytoplasm, distinct cytoplasmic borders and occasional mitoses.Interspersed among these are multinucleated osteoclastic giant cells, irregular zones of focal calcification ('chicken wire') and areas of chondroid differentiation.Also seen are ABC-like areas.
The patient had been followed up for two years with painless and complete range of motion with an X-ray showing no recurrence or lung metastasis.She has gone back to work.specimen was sent for histopathological examination which confirmed the diagnosis of chondroblastoma with areas of ABC.Postoperative patient recovery was uneventful with complete range of movements (Figure 5).
Pathological findings were as follows: grossly cut sections showed solid grey white areas with grey brown haemorrhagic areas, friable and multiple cysts were identified, exuded haemorrhagic fluid (Figure 6).Microscopy showed a solid tumour composed of a mixture of sheets of mononuclear cells and giant cells.These mononuclear cells

Licensee OA Publishing London 2013. Creative Commons Attribution License (CC-BY)
Competing interests: none declared.Conflict of interests: none declared.

All authors contributed to the conception, design, and preparation of the manuscript, as well as read and approved the final manuscript.
All authors abide by the Association for Medical Ethics (AME) ethical rules of disclosure.For citation purposes: Nithin S, Puttaswamy P. Benign chondroblastoma with secondary aneurysmal bone cyst in scapula.OA Orthopaedics 2013 Sep 09;1(2):18.

Discussion
Benign chondroblastoma is a neoplasm of chondrogenic origin predominantly occurring in the epiphysis of cylindrical bones, locally destructive lesion although metastases may occur 2,3 .The first description of chondroblastoma was given by Codman in 1931, who designated it as an 'epiphyseal chondromatous giant cell tumour'.Jaffe and Lichtenstein 1 differentiated in 1942 the chondroblastoma from giant cell tumours and established the term 'benign chondroblastoma'.Benign chondroblastoma with a secondary ABC in the inferior angle of the scapula has rarely been reported in literature.They can be secondarily involved by an ABC in 10%-15% of cases 3 .Secondary involvement of a chondroblastoma by an ABC is more likely in patients older than 20 years.
The histological diagnosis of typical chondroblastoma is usually not difficult due to their characteristic appearance with rounded or polygonal chondroblasts, multinucleated giant cells, and eosinophilic chondroid extracellular matrix with focal (chicken wire) calcification 4,5 .Scalloping or expansion of cortical bone may be present.Fine calcifications, either punctate or in rings, may be visible.Cysts are present about 20% of the time and both MRI and CT can define the fluid levels.CT is also useful for defining the relationship of the tumour to the joint, integrity of the cortex, and intralesional calcifications.Diagnosis of chondroblastoma can be arrived at by radiographs when the age of the patient and location of the lesion are seen, which are suggestive of the lesion.Nonetheless, it is important to be aware that radiographic diagnosis of an atypical chondroblastoma is more difficult 3 because of a variety of possible diagnoses, including benign and malignant lesions in the area of predilection.
The above-mentioned imaging features were highly suggestive of a benign, cystic but locally invasive process.The differential diagnosis included is mainly ABC, chondroblastic osteosarcoma, chondrosarcoma and fibrous dysplasia.Generally, ABCs present with pain and swelling of relatively rapid progression.The period between onset of symptoms and treatment is six months or less.Symptoms related to compression of adjacent structures may occasionally be present.In ABC, the feature is more sharply defined margins and has peripheral egg shell calcification indicating that the periosteum is intact around the soft tissue component (a benign radiographic feature).Intralesional fluid-fluid levels are common to both chondroblastomas and ABCs and are, therefore, not generally helpful for distinguishing the two entities.Histological examination is required to make this determination.
Conventional chondroblastic osteosarcoma most frequently (70%-80% of cases) affects tubular bones in the appendicular skeleton, particularly osseous structures around the knee (50%-75% of cases) and they usually arise in the metaphysis, and initial manifestation within the epiphysis is rare.The imaging features reflecting pathohistologically showing lace-like osteoid, abundant hyaline cartilage components, including the coexistence of bone and cartilage forming tumour matrix on radiographs, presence of lobular structure of high signal intensity on T2-weighted images, and peripheral rim and septal enhancement patterns on MRI.In these cases, the diagnosis must be made histologically in the face of conflicting radiographic data.Histologically, its difference from chondroblastoma may be extremely subtle because despite its clinically benign behaviour, chondroblastoma itself is a mitotically active, primitive tumour.Chondroblastic osteosarcomas are rare, but their accurate diagnosis is important because like their more common conventional counterparts, they may metastasise.In case of chondrosarcoma, which appears most commonly in metaphysis and the predilection age is moderately old with 30-60 years old.However, chondrosarcoma, osteosarcoma and fibrous dysplasia can't be excluded completely.So biopsy is necessary to confirm the diagnosis.
Usually the treatment of benign chondroblastoma with ABCs is intralesional curettage resection and bone grafting with possible use of adjuvant liquid nitrogen or phenol.Here, we went for enbloc resection.Excision of the tumour is sufficient in most cases 10 .In this context, the present case appears to be unique due to (1) the scapular location of the tumour, (2) diagnostic challenges and (3) treatment options.
The need for a combined and extended clinical, radiological and histological approach to the correct diagnosis of benign chondroblastoma with secondary ABC is emphasised.Chondroblastoma is a very uncommon condition.However, there may be unusual presentations in flat bones.As shown in the present patient, most of the classic criteria such as typical location and radiological appearance are not met in this case.However, the occurrence of metastatic and malignant behaviour of chondroblastoma is extremely

Figure 1 :
Figure 1: Clinical picture of the lesion over the left scapula.

Figure 5 :
Figure 5: Post operative recovery of patient.

Figure 2 :
Figure 2: Plain X-ray showing lytic lesion in inferior angle of left scapula.

Figure 3 :
Figure 3: CT scan shows an expansile lytic lesion in the infraspinous part of left scapula.

Figure 4 :
Figure 4: MRI (1.5 tesla) with contrast shows an expanding lesion in axial view.Heterogeneous on high intensity on T2 weighted image.