Journal of Oral and Maxillofacial Pathology

: 2006  |  Volume : 10  |  Issue : 1  |  Page : 10--14

Parosteal osteosarcoma of the mandible

SR Balwani, JV Tupkari, SR Barpande 
 Department of Oral Pathology and Microbiology, Government Dental College and Hospital, GHATI, Aurangabad-431 001, India

Correspondence Address:
J V Tupkari
Department of Oral Pathology and Microbiology, Government Dental College and Hospital, GHATI, Aurangabad-431 001


Parosteal Osteosarcoma, a variant of juxtacortical osteosarcoma, is seldom seen in the jaws. Here, a case of parosteal osteosarcoma of mandible in a 15-year-old female patient is presented, which occurred at the angle of mandible on the right side. The clinicopathologic features that distinguish this lesion from periosteal lesion are discussed. The contribution of computed tomography (CT) for the diagnosis is emphasized.

How to cite this article:
Balwani S R, Tupkari J V, Barpande S R. Parosteal osteosarcoma of the mandible.J Oral Maxillofac Pathol 2006;10:10-14

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Balwani S R, Tupkari J V, Barpande S R. Parosteal osteosarcoma of the mandible. J Oral Maxillofac Pathol [serial online] 2006 [cited 2022 Jun 30 ];10:10-14
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Osteosarcomas are the most common primary malignant neoplasms of bone that can occur anywhere in the body [1], but are found most often in the long bones with a predilection for the distal femoral metaphysis, proximal tibia, and humeral metaphysis [2]. It is characterized by atypical cells that produce osteoid (matrix protein produced by bone cells) [3].

Osteosarcomas arise in several clinical settings, including preexisting bone abnormalities such as Paget's disease, fibrous dysplasia, giant cell tumor, multiple Osteochondroma, bone infarct, chronic osteomyelitis, and osteogenesis imperfecta, and history of radiation exposure. Mutations or amplifications of one or more genes have been suggested by Zarbo RJ et al [4].

Head and neck Osteosarcomas are infrequent and usually present in the third and fourth decades of life, almost a decade after their presentation in long-bone tumours [1]. Approximately 6.5% of all osteosarcomas arise in the jaws, giving a rough incidence of about 1 per 1.5 million population (Garrington et al) [5].

The maxilla and mandible are involved with almost equal frequency. Mandibular tumours arise more frequently in the posterior body and horizontal ramus, whereas, maxillary tumours are discovered more commonly in the alveolar ridge, sinus floor, and palate [6].

Zarbo RJ et al have classified osteosarcomas by their site of origin into (a) the conventional type, arising within the medullary cavity; (b) juxtacortical tumours, arising from the periosteal surface; and (c) extra skeletal osteosarcomas, arising rarely in soft tissue [4].

Juxtacortical osteosarcoma, a rare bone tumour of long bones, was first described by Jaffe and Selin in 1951 [7]. Described by Geschickter and Copeland in 1951 as parosteal osteoma, it was originally thought to be a benign condition which may slowly undergo malignant change [8]. Involvement of jaw bones by juxtacortical osteosarcoma is extremely rare [9].

The purpose of this article is

1) to report a rare case of mandibular parosteal osteosarcoma,

2) to discuss differentiating features of parosteal and periosteal osteosarcoma.

 Case report

A 15-year-old female patient reported with the complaint of a painless swelling at the angle of mandible on the right side. The swelling had been present for 1 year. The swelling was initially small, gradually grew larger and reached to a size of 5.5 x 4.5 x 1.5 cm'. Medical and surgical history was not contributory.

The swelling extended superoinferiorly from 1 cm below the ala-tragus line to 0.5 cm below the lower border of mandible and antero posteriorly from the mid-point of the body of mandible to the posterior border of the ramus of mandible [Figure 1].

The swelling was roughly oval, hard in consistency, non-tender, and had a smooth surface. Borders were distinct. The overlying skin was unaffected and there were no neurological symptoms or palpable lymph nodes.

Intraorally, no abnormality was detected. The teeth on the same side of the lesion were normal ([Figure 2]

Hematological and biochemical laboratory tests were within normal limits except alkaline phosphatase level, which was elevated and was 200/100 ml plasma (king units). Haemoglobin was slightly below the normal limit and was 10.9 gm%.

The lateral oblique radiograph showed irregular diffuse bone deposition in the posterior part of the body of mandible [Figure 3] The lesional area appeared to have a patchy radiopacity and extended beyond the lower border of mandible. Few bony spicules were seen at the lower border of the lesion.

The CT scan showed an exophytic lesion over the angle of mandible [Figure 4]. The lesion consisted of irregular cauliflower like hyperdense structure of bone density [Figure 5]. Vascular proliferation was seen at the periphery of the lesion [Figure 6]. There was no evidence of cortical break or medullary extension.

The lesion was excised with healthy margins using a submandibular incision under general anesthesia. At the time of surgery, it was noted that there was no periosteal covering over the lesion and the tumour mass was found to be attached to the underlying cortex by a stalk. The tumour mass was submitted for histopathological examination.

On gross examination, the excised biopsy sample consisted of nodular mass that measured 5cm x 4cm x lcm3, hard in consistency, and yellowish to grayish white in colour. The cut surface was grayish white in colour [Figure 7].

Microscopic examination of tissue specimen was composed of well- formed bony trabeculae interspersed with malignant fibro-cellular stroma [Figure 8]. Distributed throughout the stroma were atypical spindle-shaped and polyhedral cells with hyperchromatic nuclei consistent with malignant osteoblasts [Figure 9]. The stroma contained lacelike osteoid tissue [Figure 10]. Foci of cartilaginous areas were also present.

On the basis of clinical, radiological, histopathological features, a diagnosis of "parosteal osteosarcoma of the mandible" was made.


Juxtacortical osteosarcoma represents less than 4% of all osteosarcomas and 1 % of all bone tumours (Dahlin, 1967) (8). Juxtacortical osteosarcoma (incidence of 0.07 per 100,000 population) occurs much less commonly than central medullary osteosarcoma [10].

Adekeye et al (1987) reviewed a series of 15 primary osteosarcomas and 1 metastatic osteosarcoma of the jaws and identified only one juxtacortical osteosarcoma. Regezi et al (1987) reported only 2 cases of parosteal osteosarcoma out of 17 cases of osteosarcomas and chondrosarcomas [11]. Zarbo et al (1984) suggested that juxtacortical osteosarcoma can be further subdivided into two clinicopathologic variants: parosteal osteosarcoma (low grade) and periosteal osteosarcoma (high grade) [Table 1][11],[12].

Periosteal osteosarcoma is one third to one seventh less common than parosteal osteosarcoma [2]. It has 2 to 1 male predominance and a peak occurrence at about 20 years. The lesion is usually smaller in size than the parosteal osteosarcoma and commonly involves the upper tibial metaphysis [12]. Only one of twenty-three periosteal osteosarcomas in Dahlin's series (1978) involved the mandible [11].

Radiographically, in periosteal osteosarcoma the cortex is intact and sometimes thickened, and there may be minimal tumor invasion into the cortex, without medullary involvement [13]. The involvement of the marrow tissue is helpful to differentiate between an intramedullary osteosarcoma that has permeated cortex forming a soft-tissue mass and a periosteal osteosarcoma. Periosteal osteosarcoma is more radiolucent and has a more poorly defined periphery. On occasion, the limits of the lesion may be defined by a periosteal response in the form of a Codman's triangle [12].

Histologically, periosteal osteosarcoma is composed of lobules of poorly differentiated malignant cartilage, which may show central ossification. The diagnostic pattern of fine lace-like osteoid is found in the chondroid islands and among intervening malignant spindle cells. This pattern helps to distinguish this entity from juxtacortical chondrosarcoma [12]. Chondroma and chondroid choristoma must also be considered in the microscopic differential diagnosis of periosteal osteosarcoma [11].

Local recurrence and distant metastasis may occur in periosteal osteosarcoma [12].

Parosteal osteosarcoma occurs over a wide age range and peaks at about 39 years. The tumour most commonly involves the distal femoral metaphysis and tends to be large and slow growing. It is more common in females than in males (3:2) when long bones are affected. However, in jaw bones, it is more common in males [12]. The present case was noted in a 15-year-old female patient [Table 2].

Radiographically, the parosteal osteosarcoma is characteristically radio dense and homogeneous, more at the base than at the periphery [12]. The lesion appears as a lobulated nodule attached to cortical bone by means of a short pedicle [14]. There is no radiographic continuity with the underlying marrow cavity [12]. The thin periosteal radiolucency, about 1-3 mm in width ("string sign") which separates the tumour from the subadjacent cortex, is quite characteristic but is present only in about 30% of the cases [9]. New periosteal bone formation is absent[12].

In present case, lateral oblique view showed patchy radiopacity, which extended beyond the lower border of mandible. Few fine bony spicules were present at the lower border of the lesion. The CT scan is useful to demonstrate the boundaries, attachment of the lesion to the cortex, and involvement of the marrow tissue. The CT scan of the present case showed cauliflower like growth without involvement of the marrow tissue.

Histologically, the parosteal osteosarcoma is well differentiated and is characterized by a spindle cell stroma with minimal cellular atypia and rare mitotic figures separating irregular trabeculae of bone [11]. The periphery is less ossified than the base; it may have a lobulated cartilaginous cap or may be irregular because of linear extensions into soft tissue [12].

In the present case, well-formed bony trabeculae were interspersed between malignant mesenchymal cells. Fine lacelike osteoid tissues were present among pleomorphic and hyperchromatic tumour cells. Foci of cartilaginous tissue were also present.

The bland microscopic appearance of parosteal osteosarcoma may lead to a microscopic diagnosis of osteoma, osteochondroma, Heterotopic ossification, myositis ossificans, fibrous dysplasia, or ossifying fibroma.

Therefore, a diagnosis of juxtacortical osteosarcoma requires complete synthesis of clinical, radiological, histopathological features of the tumour [11].

The parosteal osteosarcoma is generally regarded as a low-grade neoplasm that is locally aggressive and may recur if incompletely excised. It is considered to have minimal metastatic potential [12]. Local control is more limited in the maxilla than the mandible and thus mandibular osteosarcomas overall have a better prognosis than those of the maxilla [15].

Treatment of osteosarcoma has undergone a distinct change over the past few decades. Before 1970s, surgery was considered the only treatment option for osteosarcoma. Role of chemotherapy was controversial, but Jaffe, Rosen and others documented improved results with post-operative chemotherapy. Now, chemotherapy, following wide excision is the recommended treatment protocol for recurrent cases and those exhibiting highly malignant features on histological examination [9].

Unni et al (1976) reported that in long bones the prognosis for periosteal osteosarcoma is considerably more favourable than for conventional central osseous osteosarcoma, but poorer than that for parosteal osteosarcoma [11].


Juxtacortical osteosarcomas, including periosteal and parosteal subtypes, are uncommon neoplasms of the jaws. We present a case of parosteal osteosarcoma of the mandible in a 15-year-old female patient. It is important to differentiate the parosteal osteosarcoma from other types, as prognosis depends on the type of osteosarcoma.


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