Department of Pathology, University of Oklahoma Health Sciences Center
December 2007, Case 712-1.
A 6 year-old boy with a mandibular expansion.
Kar-Ming Fung, M.D., Ph.D., Glen D. Houston, D.D.S.
Department of Pathology, University of Oklahoma Health Sciences Center, Oklahoma City, OK Last update December 30, 2007
Clinical information: The patient was a 6 year-old boy. He was brought to his pediatrician because of a painless mandibular expansion on his left side. His pediatrician noted a smooth expansion in his left mandible and at the same time the first molar has not erupted over the expansion. The patient was referred to the clinic of a local dental school for treatment. On physical examination, the patient was afebrile. Development of his face and skull appear to be within normal limits except for the aforementioned expansion. There was no sign of dental infection or sinus drainage site. A panoramic view was taken and demonstrated a well defined multilocular lesion that involves the molar ramus of the left side of his mandible. The lesion was excised. The followings are representative images.
Click thumbnails to see pictures.
Pathology of the case:
The panoramic view demonstrated a mulilocular lesion in the left ramus of the mandible. The lesion is well defined and without much sclerotic changes at the rim. The first molar is unerupted and is associated with the lesion (arrow in Panel A). On histologic section, the lesion is composed of a solid mass with numerous thin, anastomosing trabecula or cords of epithelial cells. At the and of these branching anastomosis, there the epithelial component tend to expand a little and form a small island. No larger islands are noted (Panel B and C). No calcification or eosinophilic depositions are noted in the epithelial islands. There is no microcyst formation in the epithelial component and the overall pleomophism is minimal . The embedding stroma is composed of a moderately cellular, stellate shaped, rather monotonous proliferation of cells without high grade nuclear features nor mitosis.
|DIAGNOSIS: Ameloblastic fibroma.|
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smooth, evenly rounded, multilocular radiolucency with scalloped borders. The cortex is thinned and may be penetrated. Macroscopically, the cut surface is often cystic. Ameloblastoma is essentially a locally aggressive epithelial neoplasm with features of the enamel organ. There are many islands of epithelial cells with steallate stromal cells surrounded by a peripheral rim of columnar or cuboidal epithelium that resemble the enamel organ. Strongly eosinophilic, PAS(+), degenerative substances are often seen at the center of the epithelial islands. Calcifications are not uncommon. The follicular pattern characterized by discret islands of follicles of the aforementioned epithelial island or the plexiform pattern characterized by continuous anastomosing strands of the neoplastic epithelium are present. Other pattern including the unicystic, acanthomatous (with squamous cell metaplasia), granular cell type, desmoplastic, basaloid pattern, papilliferous and keratoameloblastoma. Microcyst formation is frequent and they may coalesce to form large cysts. Granular cells, which occur singly or in large masses within the follicles, replace in whole or part of the stellate reticulum may be found. The cytoplasmic granules are PAS(+). There may be substantial squamous metaplasia to suggest squamous cell carcinoma. In some cases, the vasculature is exuberant and may mimic hemangiomas.
Ameloblastic fibrosarcoma (ameloblastic sarcoma) are rare tumors and only the mesenchymal component shows features of malignancy but the epithelial compoment remains bland. These tumors can occur de novo but can also be associated with recurrent AF or ameoloblastic fibro-odontoma. There are usually no difficulties in recognizing the anaplastic features of the mesenchymal component. It should be noted that in some cases, particularly those with multiple recurrences, the mesenchymal component can dominant the histologic picture and suggest fibrosarcoma or other types of sarcomas. A high index of suspicion and diligent search for epithelial component is mandatory in order to make a correct diagnosis.
Odontoameloblastomas are extremely rare. For the cases that have been described, they happen to occur in the mandible of young patients. In contrast to AF, they are destructive lesions on radiographs and have calcifying components. Histologically, these tumors have ameloblastomatous component as wlee as odontoma-like components. Biologically, they tend to behave like ameloblastoma and characterized by multiple recurrence and local aggression.
Ameloblastic fibro-odontoma has features of AF but in addition they have enamel and dentin deposition. Ameloblastic fibro-dentinoma is best regard as a variant of ameloblastic fibro-odontoma and has only dentin deposition.
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Cases of the Month Evaluation Coordinator: KarMing-Fung@ouhsc.edu