Chondrosarcoma of the Mandible: A Challenging Lesion

Introduction

Chondrosarcoma is a cartilaginous neoplasm with varied morphological features and clinical behavior. It is a malignant tumor with pure hyaline cartilage differentiation.¹ It accounts for approximately 20% of all malignant bone tumors. The Chondrosarcomas of the maxillofacial region account for 1-3% of Chondrosarcomas of the entire body.² The overall incidence of Chondrosarcoma is 1 in 200,000 cases per year.³ There are numerous hypotheses on the origin of Chondrosarcoma. Few state that remnants of embryonic cartilage precursors from nasal development in the anterior part of maxilla and Meckel's cartilage in the posterior body of the mandible play a role.³ Others have pointed out that tumors may originate from chondrocytes, multipotent mesenchymal stem cells or embryonal chondroid.4 In head and neck region, mean age of patient ranges from 35 to 45 years and is most commonly seen in males. Maxillary jaw is affected more commonly than mandible with a ratio of 1.75:1.2 Owing to its rarity and non-specific clinical and radiographic findings, it poses a diagnostic dilemma to the oral pathologist.⁵ Histopathological examination is the gold standard for the diagnosis of Chondrosarcoma.⁶ This case involving the posterior body of mandible in a young female was a challenging case due to its unusual clinical presentation.

Case Presentation

A 27-year-old female presented with a complaint of pain in her lower right back tooth region since two months and swelling since 15 days. The swelling was initially peasized and increased to the present size in 15 days. Her medical, dental and personal history were non-relevant. A diffuse swelling was noted over her lower right side of face measuring approximately 6x4 cm extending antero-posteriorly (A-P) from 1 cm to the right side of midline to 3 cm anterior to the angle of mandible. Superioro-inferiorly (S-I), it extended from 2 cm below her ala tragus line to 1 cm beyond the lower border of mandible. Skin over the swelling appeared normal and no secondary changes were noted (Figure 1).

On palpation, the swelling was tender with no local rise in temperature. It was firm to hard in consistency with no discharge noted. Lymph nodes were not palpable. Intra oral examination revealed a diffuse swelling involving both gingivo-lingual and gingivo-buccal sulcus extending to the right side of the floor of the mouth extending A-P from mesial aspect of 32 to distal aspect of 48 crossing the midline. S-I, it extended 0.5 cm superior to occlusal surface of 46 up to the lingual sulcus (Figure 2).

The overlying mucosa appeared erythematous and was tender on palpation. The swelling was firm to hard in consistency and showed bleeding on palpation. Mobility of the involved teeth was noted. Radiographically bone loss was seen surrounding the roots of 46 in Orthopantamogram (Figure 3) and CBCT revealed perforation of the buccal cortical plate (Figure 4). The occlusal view showed a soft tissue shadow in relation to the lesion (Figure 5).

The routine blood and urine investigations were within the normal range. The differential diagnosis considered were Ameloblastoma, Aggressive ossifying fibroma, Ameloblastic carcinoma, Squamous cell carcinoma, Fibrosarcoma and Osteosarcoma based on the clinical history, findings and radiographic presentation. An incisional biopsy was performed intraorally from the lingual extension of the swelling. A single soft tissue bit measuring 2.1 x 1.5 x 1 cm was received and grossed into several bits. The microscopic examination of hematoxylin and eosin-stained section revealed parakeratinized stratified squamous epithelium and underlying connective tissue densely infiltrated with acute and chronic inflammatory cells surrounding numerous proliferating blood vessels (Figure 6). The deeper connective tissue showed sheets of cells arranged in a lobular pattern. Fibrocollagenous septa dividing the myxoid connective tissue stroma into lobules was noted where the central cells were round to polygonal in shape and peripheral cells were showing spindling. Centrally, few cells were pleomorphic and contained bizarre nucleus, some were binucleated, the mitotic figure count was 3 to 4/10 high power field, and few atypical mitotic figures were also noted (Figure 7).

Discussion

Chondrosarcomas of the head and neck region are rare and those involving the mandible are exceedingly rare entities compared to maxilla. In the mandible, posterior body in the molar region is commonly involved. It presents with vague clinical symptoms like painless to painful swelling, trismus, and mobility of the teeth. It is predominant in males than females in third to fourth decades of life.² This case is unique as it is of a young female with her mandible affected. Duration of the symptoms before diagnosis may last from few months to 35 years which include swelling, pain, paresthesia, trismus or loosening of teeth.⁷ Pain and swelling were the only complaints in this patient for a period of two months. Mucosa overlying the growth is frequently intact similar to this case.³ Radiographically, the lesion varies from completely ill-defined radiolucency to radiolucency containing radiopaque foci owing to the calcifications seen in 45% to 80% cases.⁸ Widening of periodontal ligament space known as Garrington sign may be noted. This lesion predominantly exhibited periodontal bone loss, Garrington sign and perforation of cortical plates. Chondrosarcoma is also seen in patients affected with Ollier’s disease and Maffucci’s syndrome.^7-9 These findings are non-specific, and a definitive diagnosis can only be made histologically.

On gross examination, the tumor usually appears lobular, blue to gray or gray-white, translucent with a shiny surface and is firm in consistency.¹⁰ In the present case, the growth was lobular, white in color, had a glistening surface and was firm. The histological findings of chondrosarcoma include abundant amount of hyaline cartilage with lacunae containing round to oval cells and enlarged nuclei. Cells may be arranged in clusters or in sheets.¹¹ Pleomorphic cells with atypical, bizarre nuclei, atypical spindle cells and cells with multiple nuclei may be found.¹² The cartilage may undergo calcification and eventually ossify. Chondrosarcoma causes endosteal erosion and invades the cortex, filling the haversian canal and extends into the soft tissue. The lobules of Chondrosarcoma lack the peripheral encasement by woven or lamellar bone as seen in chondroma. Hypercellularity increases with poorly differentiated tumors.⁷ This case exhibited the classic microscopic findings of chondrosarcoma as described above. There was absence of bony trabeculae or lace like arrangement of bone ruling out the possibility of chondroblastic osteosarcoma.

Grading of chondrosarcomas is done based on nuclear morphology, degree of cellularity and mitotic activity. In grade I or well differentiated Chondrosarcoma and grade II or moderately differentiated Chondrosarcoma, abundant hyaline cartilage with foci of myxoid or mucinous degeneration may be seen. The cellularity increases from grade I to II. Head and neck region most commonly exhibits Grade I Chondrosarcoma. Grade III or poorly differentiated Chondrosarcoma shows greater degree of cellularity, prominent nuclear atypia and mitosis. It is generally uncommon in any organ.^12,13 The histopathological variants of Chondrosarcoma include clear cell Chondrosarcoma, dedifferentiated Chondrosarcoma and mesenchymal Chondrosarcoma depending on the major cell types involved.⁷ The present case was diagnosed as Grade I conventional Chondrosarcoma after confirming with Ki-67 antibody IHC.

Complete surgical removal is the treatment of choice as Chondrosarcoma is a chemo resistant and radio resistant tumor.^4,6 This patient was treated by hemimandibulectomy preserving the condyle and coronoid process and reconstruction was done using a fibula graft. The post-operative healing was uneventful, and the patient is currently under follow-up. The five-year survival rate for chondrosarcomas of the jaws and facial bones has been reported to be 43 to 95%.⁷ Metastasis is not very common in head and neck cases nor was found in this case. The presented case was of a low-grade Chondrosarcoma involving the body of the mandible with non-specific clinical and radiographic presentation. The histological evaluation was characteristic and played a crucial role in the diagnosis. This report shows that routine hematoxylin and eosin staining is sufficient to establish the diagnosis of Chondrosarcoma. This case report signifies the role of an Oral Pathologist who can diagnose such rare cases with sufficient knowledge and thorough observation, thereby referring the patient at the earliest to cancer care centers to improve the survival rate.

Conflicts of interest

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Acknowledgements

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