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Odontogenic carcinosarcoma of the mandible: a case report and review

Odontogenic carcinosarcoma is an extremely rare malignant odontogenic tumor with only a few reported cases. It is characterized by a true mixed tumor showing malignant cytology of both epithelial and mesenchymal components. It has been assumed to arise from pre-existing lesions such as ameloblastoma, ameloblastic fibroma, and ameloblastic fibrosarcoma. To date, the reported cases have exhibited considerably aggressive clinical behavior. The case of an odontogenic carcinosarcoma in the mandible of a 61-year-old male is described herein. The tumor destroyed the cortex of the mandible and invaded the adjacent tissues. Treatment was performed by surgical resection and reconstruction. The purposes of this article are to introduce odontogenic carcinosarcoma through this case study, to distinguish it from related diseases and to discuss features of the tumor in the existing literature.


I. Introduction
Odontogenic carcinosarcoma is an extremely rare malignant tumor that is a mixture of odontogenic carcinoma and sarcoma, such that both epithelial and mesenchymal components show malignant activity [1][2][3][4][5] . Odontogenic neoplastic potential correlates with odontogenesis. Odontogenesis depends on the close interaction of epithelial and mesenchymal tissues 4,6 . Either purely epithelial or mesenchymal or a mixture of both tissues may form neoplastic lesions. Clinically, the tumor presents with aggressive, recurrent and metastasizing features [1][2][3][4][5] . Treatment is primarily surgical resection, though an adjuvant therapy may be necessary.
Odontogenic carcinosarcoma is related with some tumors such as ameloblastoma, ameloblastic fibroma, ameloblastic fibrosarcoma, and osteosarcoma. Etiologically, the aforementioned lesions may affect the pathogenesis of odontogenic biopsy revealed a linear core of tissue consisting of delicate trabeculae of woven bone in fibrous stroma and no epithelial element. (Fig. 4) The diagnosis of the tibial lesion was fibrous dysplasia, and seemed to be irrelevant to oral cancer. Nevertheless, the possibility of distant metastasis could not be completely excluded by CT guided biopsy. Therefore, surgery and excisional biopsy for the tibial lesion was recommended, but the patient refused the procedure.
On September, 2011, segmental resection including wide excision of the surrounding soft tissues was performed by a left partial mandibulectomy. After evaluation of the panoramic view, oropharynx CT and oropharynx MRI, a margin of more than 1.5 cm was decided for safety. Simultaneously, a left regional lymph nodes (Level I to partially Level III) was removed in a mass by selective neck dissection. (Fig. 5) The mandibular condyle was preserved and the position of an intramedullary osteolytic lesion in the proximal diaphysis of the tibia with a thin sclerotic rim on MRI images of the right tibia. Subsequently, computed tomography (CT) guided and strands similar to ameloblastoma, the tumor cells were obviously malignant cells showing aberrant cytologic atypia, hyperchromasia, and abnormal mitoses. (Fig. 7. A) The mesenchymal component was morphologically consistent with sarcoma showing marked pleomorphism, enlarged hyperchromatic nuclei, and increased nuclear-to-cytoplasmic ratio. (Fig. 7. B) The tumor also invaded into surrounding skeletal muscle and connective tissue. As a whole, these pathologic findings confirmed the diagnosis of odontogenic carcinosarcoma. This diagnosis was supported by positive immunohistochemistry for cytokeratin and CAM 5.2 of carcinomatous element and for vimentin of sarcomatous element. (Fig. 8)

III. Discussion
Odontogenic carcinosarcoma was defined by the 1992 the mandible was stabilized by a reconstruction plate with a right iliac bone graft. (Fig. 6. A) On histopathologic examination, all the margins were free of tumor infiltration with no metastatic tumor in the lymph nodes; the final diagnosis was changed to odontogenic carcinosarcoma. After the operation, the patient had a favorable reconstruction result without significant complications. On March 2012, the operation for removal of the reconstruction plate and internal fixation devices was performed. (Fig. 6. B) Histopathologically, a few soft tissues around the fixation device were identified as inflammatory granulation tissue, but tumor recurrence was not present.
Up to now, the patient continues to do well postoperatively. Sections from representative areas of the tumor were stained with H&E. Immunohistochemical studies were also performed using cytokeratin, CAM 5.2, and vimentin. The H&E-stained sections disclosed an invasive tumor consisting of epithelial and mesenchymal neoplastic components. Although the epithelial neoplastic component showed nests Extremely rare lesion and related neoplasms such as ameloblastoma, ameloblastic fibroma, ameloblastic fibrosarcoma, and osteosarcoma are summarized in Table 1 to avoid confusion later on. They occur mainly in the mandible, are seen equally in both sexes, and have high recurrence rates except for osteosarcoma. Furthermore, the tumors may arise de novo or from pre-existing lesions. De novo odontogenic tumors arise from remnants that originated in the embryologic pro- odontogenic carcinosarcoma has distinctively malignant activity in both components and high potential of metastasis. In general, these tumors are primarily treated by surgical resection. The effectiveness of adjuvant therapy remains controversial. In particular, radiation therapy carries the possibility of inducing oncogenesis, and ameloblastic series have potential capacity for the radiation resistance 8 . In other words, adjuvant therapy may contribute to recurrence and malignant transformation.
Given the scarcity of reported cases, odontogenic carcinosarcoma is difficult to characterize. In a retrospective study of a few cases ( Table 2) 1-5 , the patients' ages ranged from 9 to 63 years, and there was no gender preference. It was more common in the mandible, and mainly believed to progress from related neoplasms. The pathogenesis of malignant transformation is not completely understood, but it is considered to occur after multiple recurrences and surgical treatments. Nevertheless, the tumor may arise de novo such as in the present case without previous disease and surgical intervention.
In previously published cases, the tumor has a fatality rate of more than 50% with high rates of recurrence and metastasis. Aside from two cases, all the other patients died. However, DeLair et al. 4 and present cases without evidence of recurrence or metastasis after the first operation without use of adjuvant therapy. Moreover, the clinical behavior of the tumors was favorable. Due to the short follow-up period in these 2 cases, these results were not able to be confirmed.
In summary, this is a case report of a rare occurrence of odontogenic carcinosarcoma. This malignant tumor shows mixed features of both carcinomatous and sarcomatous elements on histopathological study, and is clinically very aggressive features with high rates of recurrence and metastasis. However, the current case resulted in a favorable clinical prognosis. If the tumor is detected at an early stage and has mild features, then adequate surgical treatment alone may lead to good outcomes. A larger number of cases and prolonged follow-up are need to further clarify the nature of odontogenic carcinosarcoma.

Conflict of Interest
No potential conflict of interest relevant to this article was reported.