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Presented by William Westra, M.D. and prepared by Bahram R. Oliai, M.D.
Case 6: 74 year-old man with a large mass involving the maxillary sinus and underlying palatine bone.
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1. Question
Week 86: Case 6
74 year-old man with a large mass involving the maxillary sinus and underlying palatine bone.images/1030a.jpg
images/1030b.jpg
images/1030c.jpgCorrect
Answer: Ameloblastoma
Histology: The lesion is solid without a cystic component. It is comprised of large anastomosing islands of cells. The centers of these islands are made up of cells with abundant pink cytoplasm and keratin pearl formation. On close inspection, palisaded and polarized columnar cells border the islands. There is no significant pleomorphism, and mitotic figures are not readily found. The intervening stroma is highly collagenized.
Discussion: Ameloblastoma is a benign but locally aggressive neoplasm of odontogenic epithelial origin. It bears histologic resemblance to the enamel organ. It is microscopically recognized by a peripheral border of palisaded and polarized columnar cells, and a central zone of stellate reticulum-like cells. The stellate reticulum cells are unevenly dispersed polygonal to fusiform cells. These cells may undergo transformation into cells with prominent granular cytoplasm (granular cell variant) or into cells showing squamous differentiation (acanthomatous variant). When squamous differentiation is prominent as in the present case, ameloblastomas can be mistaken for squamous cell carcinoma, particularly when there is extension beyond bone or when these tumors arise in an extraosseous location (i.e. peripheral ameloblastoma). Key to avoiding this diagnostic pitfall is the recognition of the peripheral layer of pallisaded and polarized cells. Furthermore, the squamous island in the acanthomatous variant of ameloblastoma lack overtly malignant cytologic features. We have also seen cases where ameloblastomas have been mistaken for aggressive inverted schneiderian papillomas. Like some ameloblastomas, inverted papillomas often are characterized by interconnected islands and lobules of epithelial cells. In contrast to ameloblastoma, inverted papillomas of the sinonasal tract usually demonstrate a surface epithelial component, intraepithelial neutrophils and intraepithelial mucin cysts; and they lack a stellate reticulum.
Ameloblastomas may recur if inadequately excised. Depending on size, location and surgical philosophy, the extent of resection varies from simple enucleation to complete tumor resection with a zone of surrounding normal bone.
Incorrect
Answer: Ameloblastoma
Histology: The lesion is solid without a cystic component. It is comprised of large anastomosing islands of cells. The centers of these islands are made up of cells with abundant pink cytoplasm and keratin pearl formation. On close inspection, palisaded and polarized columnar cells border the islands. There is no significant pleomorphism, and mitotic figures are not readily found. The intervening stroma is highly collagenized.
Discussion: Ameloblastoma is a benign but locally aggressive neoplasm of odontogenic epithelial origin. It bears histologic resemblance to the enamel organ. It is microscopically recognized by a peripheral border of palisaded and polarized columnar cells, and a central zone of stellate reticulum-like cells. The stellate reticulum cells are unevenly dispersed polygonal to fusiform cells. These cells may undergo transformation into cells with prominent granular cytoplasm (granular cell variant) or into cells showing squamous differentiation (acanthomatous variant). When squamous differentiation is prominent as in the present case, ameloblastomas can be mistaken for squamous cell carcinoma, particularly when there is extension beyond bone or when these tumors arise in an extraosseous location (i.e. peripheral ameloblastoma). Key to avoiding this diagnostic pitfall is the recognition of the peripheral layer of pallisaded and polarized cells. Furthermore, the squamous island in the acanthomatous variant of ameloblastoma lack overtly malignant cytologic features. We have also seen cases where ameloblastomas have been mistaken for aggressive inverted schneiderian papillomas. Like some ameloblastomas, inverted papillomas often are characterized by interconnected islands and lobules of epithelial cells. In contrast to ameloblastoma, inverted papillomas of the sinonasal tract usually demonstrate a surface epithelial component, intraepithelial neutrophils and intraepithelial mucin cysts; and they lack a stellate reticulum.
Ameloblastomas may recur if inadequately excised. Depending on size, location and surgical philosophy, the extent of resection varies from simple enucleation to complete tumor resection with a zone of surrounding normal bone.
