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Ameloblastic carcinoma is a rare locally aggressive odontogenic epithelial neoplasm or malignant epithelial odontogenic tumor of the maxillofacial skeleton with a distinct predilection in the mandible that normally begins in the bones of the jaw that originate from pre-existing ameloblastoma of the odontogenic cyst. Two-thirds of these tumors arise from the mandible while one-third originate in the maxilla [6]. It is classified as an odontogenic tumor, meaning that it arises from the epithelium that forms the enamel of the teeth. The pattern of epithelial growth is similar to the developing tooth germ and distinctive enough to separate it from other epithelial malignancies. Symptoms may include progressive pain and swelling of the jaw. Ameloblastic carcinoma may spread (metastasize) to affect other organs of the body.
Carcinoma refers to a malignancy that arises from the epithelium. For instance carcinoma of the skin is termed ‘squamous cell carcinoma’ and carcinoma from glandular epithelium is termed ‘adenocarcinoma’. The term “cancer” refers to a group of diseases characterized by abnormal, uncontrolled cellular growth that invades surrounding tissues and may spread (metastasize) to distant bodily tissues or organs via the bloodstream, the lymphatic system, or other means. Different forms of cancer, including odontogenic tumors, are classified based on the cell type involved, the specific nature of the malignancy, and the disease’s clinical course.
The ameloblastoma is an odontogenic tumor of the jaws, arising from dental embryonic remnants possibly from the epithelial lining of an odontogenic cyst; dental lamina or enamel organ; stratified squamous epithelium of the oral cavity; or displaced epithelial remnants [rx]World Health Organisation (WHO) classification of Head and Neck tumors (2005), ameloblastic carcinoma is categorized into three main subtypes; primary type, secondary type (dedifferentiated) intraosseous and secondary type (dedifferentiated) peripheral [rx]. Primary tumors arise de novo, whereas the second type represents the malignant transformation of pre-existing well-differentiated ameloblastoma of the odontogenic cyst. We present a rare case of mandibular ameloblastic carcinoma, secondary type (de-differentiated) intraosseous in previously untreated ameloblastoma.
Causes
The exact cause of ameloblastic carcinoma is unknown. Most cases arise spontaneously without a previous history of cancer (de novo). Researchers speculate that genetic and immunologic abnormalities, environmental factors (e.g., exposure to ultraviolet rays, certain chemicals, ionizing radiation), diet, stress, and/or other factors may play contributing roles in causing specific types of cancer. Investigators are conducting ongoing basic research to learn more about the many factors that may result in cancer.
In individuals with cancer, malignancies may develop due to abnormal changes in the structure and orientation of certain cells known as oncogenes or tumor suppressor genes. Oncogenes control cell growth; tumor suppressor genes control cell division and ensure that cells die at the proper time. The specific cause of changes to these genes is unknown. However, current research suggests that abnormalities of DNA (deoxyribonucleic acid), which is the carrier of the body’s genetic code, are the underlying basis of cellular malignant transformation. These abnormal genetic changes may occur spontaneously for unknown reasons or, more rarely, may be inherited. In ameloblastic carcinoma, no genetic predisposition has been identified.
Ameloblastic carcinoma may develop from the epithelial tissue that remains after the development of the teeth and associated structures. In some cases, it results from the malignant transformation of existing ameloblastoma or a benign odontogenic cyst.
Diagnosis
A diagnosis of ameloblastic carcinoma is made based upon a thorough clinical evaluation, a detailed patient history, and a microscopic examination of the tumor. Most cases are found incidentally. One procedure is known as fine needle aspiration, in which a thin, hollow needle is passed through the skin and inserted into the nodule or mass to withdraw small samples of tissue for study.
In addition to biopsies, various x-ray techniques may be used to help evaluate the size, placement, and extension of the tumor and to serve as an aid for future surgical procedures. Such imaging techniques may include computerized tomography (CT) scanning and magnetic resonance imaging (MRI). During CT scanning, a computer and x-rays are used to create a film showing cross-sectional images of certain tissue structures. An MRI uses a magnetic field and radio waves to produce cross-sectional images of particular organs and bodily tissues. Laboratory tests and specialized imaging tests may also be conducted to determine possible infiltration of regional lymph nodes and the presence of distant metastases.
Treatment
The therapeutic management of individuals with ameloblastic carcinomas may require the coordinated efforts of a team of medical professionals, such as physicians who specialize in the diagnosis and treatment of cancer (medical oncologists), specialists in the use of radiation to treat cancer (radiation oncologists), dental specialists, surgeons, oncology nurses, and other specialists.
Specific therapeutic procedures and interventions may vary, depending upon numerous factors, such as primary tumor location, the extent of the primary tumor (stage), degree of malignancy (grade); whether the tumor has spread to lymph nodes or distant sites; individual’s age and general health; and/or other elements. Decisions concerning the use of particular interventions should be made by physicians and other members of the health care team in careful consultation with the patient, based upon the specifics of his or her case; a thorough discussion of the potential benefits and risks; patient preference; and other appropriate factors.
Wide surgical excision provides the best chance of controlling the tumor. Adjunctive radiation may be used however radiation treatment has not been effective as a primary form of therapy. Radiation therapy may also be performed before surgery to decrease tumor size. Recurrence of ameloblastic carcinoma after surgical removal may occur and may involve various organs in the body with or without recurrence in the jaw. Most common recurrences are seen in the same area as the original tumor. Recurrence may occur within a year of surgery or several years later. Because of the risk of recurrence, life-long periodic physical examinations are necessary.
Chemotherapy has not proven effective in treating individuals with ameloblastic carcinoma and is most often used to try and control widespread metastases. Developing the optimal treatment for individuals with ameloblastic carcinoma has been hindered because of the relatively few identified cases.
In June 2013, the patient underwent a right supraomohyoid neck dissection, right hemi-mandibulectomy (condyle sparing) via a midline lip-split, and right anterolateral thigh free-flap reconstruction for defect closure. Bony reconstruction was not considered appropriate given his performance status, habitus, and co-morbidities.
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