Oncol. Gastroenterol. Hepatol. Reports Vol.1 / Issue 1 / Jul–Dec, 2012 41

Case Report O G H Re p o r t s

Chondroblastic osteosarcoma of proximal fibulaYasir Salam Siddiqui,1* Pathania VP,1 Manisha Mendiratta,2 Nusra Rahman3

1Dept. of Orthopaedic Surgery, SRMS - Institute of Medical Sciences, Bhojipura, Bareilly, UP, India2Dept. of Pathology, SRMS - Institute of Medical Sciences, Bhojipura, Bareilly, UP, India and - 1Junior Resident, Dept. of Anatomy3J.N. Medical College, AMU, Aligarh, UP, India

INTRODUCTION

Osteosarcoma is the most common form of primary malignant bone tumour that occurs during childhood and adolescence. The incidence of new diagnoses peaks in the second decade of life. Osteosarcoma most com-monly develops at sites of rapid bone turnover, such as the distal femur, proximal tibia, and proximal humerus. Less common sites for osteosarcoma include the pelvis, the spine, and the craniofacial bones. The proximal fib-ula is a relatively rare site for osteosarcoma and in Mayo series reported incidence was only 2%.[1] Radiologically, osteosarcoma typically presents as osteoblastic and/or osteolytic lesion with ill-defined borders and associated soft-tissue mass. Treatment typically includes preopera-tive chemotherapy, surgical resection, and postoperative chemotherapy. Limb-salvage procedures with wide sur-gical margins are the mainstay of surgical intervention.

The management of osteosarcoma of the proximal fibula is demanding for the treating surgeon because of the proximity of the common peroneal nerve to the lesion. Resection of malignant tumours often requires wide sur-gical margins and to obtain such margin, at times resec-tion of the common peroneal nerve is done. The purpose of this case report is to discuss the difficult aspects of diagnosis and management of osteosarcoma of proximal fibula. The case report is presented after obtaining informed consent from the patient.

CASE REPORT

A 17 year old male patient presented to our institu-tion with 5 months history of gradually increasing pain and swelling in the region of his right proximal leg. He did not give any history of trauma, fever or any other systemic illness. Examination revealed firm and tender swelling involving the proximal fibula. Movements of the knee were within normal limits. Common peroneal nerve was intact. The patient’s laboratory results were normal except for low levels of haemoglobin, elevated levels of lactate dehydrogenase and alkaline phosphatase. Plain radiographs of the right knee showed the inter-rupted periosteal reaction involving the meta-diaphysis of proximal fibula. The lesion seems to have infiltrated

*Corresponding address: Dr. Yasir Salam Siddiqui Assistant Professor, Dept. of Orthopaedic Surgery SRMS - Institute of Medical Sciences, Bhojipura, Bareilly, UP, India Mobile: +919837343400, Fax: 00915712702758Email: yassu98@gmail.com

DOI: 10.5530/ogh.2012.1.10

ABSTRACT

Osteosarcoma is the most common form of primary malignant bone tumour that occurs during childhood and adolescence. The incidence of new diagnoses peaks in the second decade of life. The metaphysis of the long bones is the site of predilection, and, in declining order, it commonly involves distal femur, proximal tibia, and proximal humerus. The proximal fibula is a relatively rare site for osteosarcoma. We are reporting a case of osteosarcoma of proximal fibula in a 17-year-old male child and discuss the difficult aspects of diagnosis and management.

Keywords: Chondroblastic osteosarcoma, bone tumour, metaphysis.

Yasir Salam Siddiqui, et al.: Chondroblastic osteosarcoma of proximal fibula

42 Oncol. Gastroenterol. Hepatol. Reports Vol.1 / Issue 1 / Jul–Dec, 2012

the surrounding soft tissues, but proximal epiphysis of fibula seems to be free of the lesion (Figure 1). Inter-rupted periosteal reaction and extension of lesion in soft tissues indicated the aggressiveness of the lesion. Chest X-ray did not reveal any metastatic deposit. CT-scan of the chest was also normal. Magnetic resonance imag-ing (MRI) of the lesion also showed aggressive lesion involving the anterolateral aspect of proximal fibula. MRI also revealed irregular cortex and cortical breach with extension of the lesion in surrounding soft tissues (Figure 2 and 3). Common peroneal nerve was free of lesion as it lies posterior to fibular head. A clinico- radiological diagnosis of aggressive neoplastic lesion involving proximal fibula was made and the lesion was subjected to Fine Needle Aspiration Cytology (FNAC), to establish histological diagnosis. FNAC report was incon-clusive. Considering the aggressive nature of lesion, exci-sion of the lesion along with resection of the proximal fibula with safe margins was planned. During operation, it was found that the lesion had expanded the proximal end of fibula, and had infiltrated the surrounding soft tissues. The lesion along with the infiltrated soft tissues with safe margins was excised (Figure 4) and sent for his-tological examination. Common peroneal nerve was not resected as MRI and clinical examination excluded the involvement of nerve by tumorous lesion. No attempt was made to reconstruct the lateral soft tissue structures. Biopsy report showed areas of chondroid and osteoid dif-ferentiation, with predominance of neoplastic chondro-cytes in the form of lobules. At the periphery of cartilage there are spindle cells with areas of new bone formation- osteoid matrix. The final biopsy report established

diagnosis of chondroblastic osteosarcoma. Immediate post-operative period was uneventful with preservation of ankle dorsiflexion, but the patient developed toes drop. Patient was given 6 cycles of multi-agent chemo-therapy, following confirmation of diagnosis of chon-droblastic osteosarcoma. At the latest follow-up patient is not having any clinico-radiological (Figure 5) evidence

Figure 1. Plain radiographs of the right knee showed the in-terrupted periosteal reaction involving the meta-diaphysis of proximal fibula (arrow heads). The lesion seems to have infil-trated the surrounding soft tissues, but proximal epiphysis of fibula seems to be free of the lesion.

Figure 2. Magnetic resonance imaging (MRI) of the lesion showed aggressive lesion involving the anterolateral aspect of proximal fibula. MRI also revealed irregular cortex and cortical breach with extension of the lesion in surrounding soft tissues (thick arrows). MRI also clearly showed sparing of proximal epiphysis of fibula (thin arrow).

Figure 3. Magnetic resonance imaging (MRI) of the lesion showed aggressive lesion involving the anterolateral aspect of proximal fibula. MRI also revealed irregular cortex and cortical breach with extension of the lesion in surrounding soft tissues (arrows).

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Oncol. Gastroenterol. Hepatol. Reports Vol.1 / Issue 1 / Jul–Dec, 2012 43

of local recurrence or metastasis. Continuous follow-up for the possibility of local tumour recurrence and dissemination of the disease should be emphasized in these patients.

DISCUSSION

Osteosarcoma is the most common primary malig-nant bone tumour in children and adolescents.[2] The

proximal fibula is a rare site of osteosarcoma represent-ing about 2% of all osteosarcomas. In previous reports on osteosarcoma arising from the proximal fibula, most of the patients were in their second decade,[3–6] which was also seen in our patient. As resection of malignant tumours frequently necessitates wide surgical margins, in this view the treatment of sarcoma of the proximal fibula carries difficulties firstly, because of the frequent involvement of the peroneal nerve and resultant foot drop following resection of nerve to achieve clear margins. Secondly, stability of the knee joint is also at stake following resection of tumour. In our patient we intentionally preserved the common peroneal nerve as some authors have reported good results by preserving the common peroneal nerve through intentional mar-ginal excision of these tumours.[4,5] In our patient, even though no attempt was made to reconstruct the lateral soft tissue structures providing knee stability, postopera-tively the knee was stable and with good function. This was in confirmation with authors who have reported good function after resection without ligament recon-struction.[3]

The current World Health Organization (WHO) classifi-cation of osteosarcoma recognizes three major subtypes of conventional osteosarcoma: osteoblastic, chondroblas-tic, and fibroblastic, reflecting the predominant type of matrix in the tumour.[7] Chondroblastic osteosarcoma and conventional osteosarcoma have similar clinical, radiolog-ical, and prognostic features. Chondroblastic osteosarco-mas constitute 9–25% of conventional osteosarcomas.[8] Morphologically, they are characterized with chondroid and osteoid differentiation. Chondroblastic osteosarcoma can be confused with chondrosarcoma in small biopsy specimens, and differentiating it from chondroblastic osteosarcoma is difficult. Osteoid formation within the tumour is the most important morphologic diagnostic feature. It is not always possible to obtain osteoid forma-tion in small biopsy specimens. As a consequence, cases with chondroblastic osteosarcoma might be misdiag-nosed as chondrosarcoma. False diagnosis rate has been reported to be as high as 44%.[9] Hence, clinico-radiolog-ical findings must be used for differentiating chondro-blastic osteosarcoma from chondrosarcoma. The most important clinical findings are patient’s age and location of the lesion. As in our case, the radiological differential diagnosis of an atypically located lesion in proximal fibula in a teenager was osteosarcoma and Ewing’s sarcoma. Chondrosarcoma was not kept in differential diagnosis on clinico-radiological ground. Unni emphasized that in an adolescent patient, if the tumour morphologically constitutes a neoplastic cartilage and osteoid formation

Figure 4. Clinical photograph of resected proximal fibula showing glistening white tumoral mass causing breach and expan sion of proximal fibula.

Figure 5. Plain radiographs of the right knee showing exci-sion of proximal fibula with no evidence of recurrence.

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44 Oncol. Gastroenterol. Hepatol. Reports Vol.1 / Issue 1 / Jul–Dec, 2012

does not accompany, unless established to the contrary, it must be considered and treated as chondroblastic osteosarcoma.[8] In our case biopsy clearly showed asso-ciation of neoplastic cartilage with malignant osteoid, establishing diagnosis of chondroblastic osteosarcoma and subsequent multi-agent chemotherapy resulted in good functional outcome.

A systematic approach to clinical history, radiographic evaluation and histopathology is necessary for accu-rate diagnosis of osteosarcoma. Our result showed that after resection of the proximal fibula the knee function remained stable, even though no attempt was made to reconstruct the lateral soft tissue structures. Peroneal nerve-preserving surgery is associated with a high risk of local recurrence and continuous follow-up for the possibility of local tumour recurrence and dissemi-nation of the disease should be emphasized in these patients.

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3. Einoder PA, Choong PF. tumors of the head of the fibula: good function after resection without ligament reconstruction in 6 patients. Acta Orthop Scand 2002;73:663–6.

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