|Year : 2015 | Volume
| Issue : 3 | Page : 660
Atypical giant chondroblastoma mimicking a chondrosarcoma
Sunita Dhanda1, Santosh Menon2, Ashish Gulia3
1 Department of Radiology, Tata Memorial Centre, Dr. Ernest Borges Marg, Parel, Mumbai, Maharashtra, India
2 Department of Pathology, Tata Memorial Centre, Dr. Ernest Borges Marg, Parel, Mumbai, Maharashtra, India
3 Department of Orthopedic Oncology, Tata Memorial Centre, Dr. Ernest Borges Marg, Parel, Mumbai, Maharashtra, India
|Date of Web Publication||9-Oct-2015|
Department of Radiology, Tata Memorial Centre, Dr. Ernest Borges Marg, Parel, Mumbai - 400 012, Maharashtra
Source of Support: None, Conflict of Interest: None
Chondroblastoma is a rare, benign tumor derived from chondroblasts, commonly presenting in the second decade of life. It is usually found in the epiphysis or apophysis of long bones; however, it may rarely affect flat bones like scapula. Occasionally a histologically typical chondroblastoma may exhibit an aggressive behavior that is not normally associated with benign tumors such as a large size, pulmonary metastases, joint and soft-tissue infiltration and local recurrence. We present a case report of a patient with chondroblastoma showing atypical radiological presentation and non-concordance with age.
Keywords: Acromion, atypical, chondroblastoma, chondroid matrix, giant
|How to cite this article:|
Dhanda S, Menon S, Gulia A. Atypical giant chondroblastoma mimicking a chondrosarcoma. J Can Res Ther 2015;11:660
| > Introduction|| |
Chondroblastoma is a rare, benign cartilaginous tumor of adolescents and young adults. It usually arises from the epiphysis or apophysis of long bones; however it may rarely affect unusual sites such as flat bones, small bones and temporal bone. Chondroblastoma of the scapula is extremely rare. , Here we report a case of chondroblastoma of scapula which was not only giant in size, but also manifested late in life.
| > Case report|| |
This was a case report of a 63-year-old male patient who presented with a history of insidious onset, gradually progressive swelling and pain of the left shoulder for the last 10 years. On physical examination, a non-tender, hard swelling measuring approximately 11 × 7 cm in size was noted at the tip of the left shoulder. Shoulder movements were painful with a limited range of abduction. There was no evidence of cervical or axillary lymphadenopathy. No clinical evidence of neurovascular involvement was noted. There was slight atrophy of the deltoid and rotator cuff muscles on the affected side.
Plain radiograph of the left shoulder [Figure 1]a and b revealed a grossly expansile lytic lesion involving the entire acromion process of the left scapula with marked cortical thinning. Cortex was imperceptible at certain places. The lesion showed extensive flocculent pattern of calcification consistent with a chondroid matrix. No periosteal reaction or associated extra-osseous soft tissue mass was noted. Rest of the scapula and proximal humerus were uninvolved. Acromioclavicular and glenohumeral joints were preserved.
|Figure 1: Frontal (a) and oblique (b) radiographs of the left shoulder joint reveal a grossly expansile lytic lesion of the acromian process with marked cortical thinning. Punctate and flocculent chondroid pattern of matrix calcification is noted|
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J needle biopsy of the mass revealed a low grade chondroid lesion. The case was discussed at the multidisciplinary meeting. Based on the patient's age, lesion location, chondroid pattern of matrix mineralization and giant size of the lesion, a consensus pre-operative diagnosis of chondrosarcoma was made. No other differential diagnosis was considered. Patient underwent magnetic resonance imaging (MRI) for local staging and computed tomography (CT) of thorax to evaluate for any pulmonary metastases. CT scan of thorax demonstrated a chondroid lesion of the left acromion process with marked cortical thinning. There was no extra-osseous soft tissue mass. No evidence of pulmonary or mediastinal nodal metastases was seen. MRI revealed a lobulated soft-tissue mass of the acromion, showing isointense signal to muscle on T1 and hyperintense signal on T2-weighted images. There was no intra-articular extension into the left acromio-clavicular joint. No skip lesions were detected. In view of the combined clinical, radiologic and histologic review, en-bloc scapulectomy was agreed upon as the treatment of choice.
En-bloc resection of the scapula was performed. Histopathological examination [Figure 2] of the excised specimen revealed cellular tumor with interspersed hyalinized areas within. The cellular foci comprised of small to medium size cells with nuclear grooves and moderate cytoplasm. Focal pathognomonic chicken wire calcification was noted. These microscopic features were compatible with the diagnosis of a benign chondroblastoma. S100 immunohistochemical stain was performed on the surgical specimen, which was strongly positive. Chondrosarcoma was excluded based on the presence of only sparse mitosis without any atypical cellular hyperplasia.
|Figure 2: Histopathology of the giant chondroblastoma (H and E, original magnification ×100) demonstrating a cellular neoplasm with oval to round cells, some with nuclear grooves and the characteristic "chicken wire" calcification (arrow)|
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| > Discussion|| |
Chondroblastoma is an uncommon benign cartilaginous primary bone tumor with an overall incidence less than 1% of primary bone tumors.  It typically involves the epiphysis or apophysis of long tubular bones. ,,, However, it may rarely affect unusual sites such as flat bones, small bones and temporal bone.  The tumor has a preference for males over females (male-to-female ratio 2:1). 90% of the lesions are reported to occur in patients aged 3-25 years.  It is rare in elderly patients. In this age group, it predominantly arises at atypical sites, as was also seen in our case.  Although chondroblastoma is a benign lesion, it may show aggressive features such as large size, pulmonary metastases, joint and soft-tissue infiltration and local recurrence.  It shows a more aggressive behavior in the flat bones than in the long bones. 
Clinically, the lesions present with pain and decreased range of motion due to incitation of inflammatory changes in the surrounding tissues.  Giant lesions may present as palpable lumps.  Although the size may vary, average size at presentation is 3-5 cm.  The lesion size was large in our case, measuring approximately 11 cm in the maximum dimension. This giant variant of chondroblastoma is quite rare.
Classically, on plain radiograph, chondroblastoma presents as an eccentric expansile lytic lesion involving the epiphysis or apophysis of a long tubular bone, which may have an extension into adjacent metaphysis. It is lobulated, with sclerotic margins and areas of calcification in about a third of the cases. A rim of cortical bone is usually seen at the periphery of the tumor. 
MRI features of chondroblastoma are non-specific. It shows intermediate signal intensity on T1 and high signal intensity on T2-weighted images with a halo of bone edema. CT scan is superior to plain radiographs for detection of typical chondroid matrix calcifications, which are demonstrable in up to 60% of the cases. A chondrosarcoma cannot be excluded in a Lodwick's Ib or Ic lesion with flocculent matrix calcifications as was also the pitfall in our case. 
The standard treatment for chondroblastoma is curettage or marginal resection with or without bone grafting. , It is curative in most cases with reported recurrence rates of 10-35%. Recurrence is more common when the localization is atypical.  Adverse effects of surgery in younger patients include injury to the articular surface or adjacent unfused growth plates leading to growth disturbance, decreased range of motion and premature arthritis. Percutaneous RF ablation has been reported as an alternative to surgery for treatment of small sized chondroblastomas. Larger lesions beneath weight-bearing surfaces are at an increased risk of articular collapse and recurrence following this procedure. 
Although histological diagnosis of typical chondroblastoma is usually not difficult; in our case; patient's age, lesion size, location and radiographic appearance added to the confusion and prevented the multidisciplinary team from considering any pre-operative diagnosis other than a chondrosarcoma. Clinical and radiographic features were unusual for a chondroblastoma. A repeat tru-cut biopsy under CT guidance for sampling another tumor region was not considered as it would not have altered the surgical decision of an en-bloc scapular resection. In view of the lesion size and location, a meticulous intralesional curettage and bone grafting would have been difficult to achieve, even if a pre-operative diagnosis of a benign chondroblastoma had been made.
| > Summary|| |
Our case highlights how a giant benign chondroid lesion with flocculent matrix mineralization in a flat bone of an elderly patient could be easily mistaken clinicoradiologically for a malignant lesion like chondrosarcoma. Most of the classic criteria for a chondroblastoma such as patient's age, lesion location and radiographic appearance were not met in our case. Hence, a high index of suspicion on imaging and careful pre-operative biopsy evaluation is essential prior to surgical management of such scapular lesions. Incorrect diagnosis of chondrosarcoma may lead to inadvertent radical surgical management which may cause functional impairment to the patient, whereas chondroblastoma which is a benign cartilaginous tumor is treated by bone curettage with or without bone grafting. This might help to preserve functionality of the involved anatomy. However, in case of giant lesions in unusual locations such as ours, intralesional curettage may be incomplete and biological behavior remains uncertain which may result in high recurrence rates and hence a wide en-bloc excision is preferred.
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[Figure 1], [Figure 2]