Pathology

MICROSCOPIC DESCRIPTION:

Sections show fibroadipose tissue with two lymph nodes. One lymph node contains a 12mm maximum dimension well demarcated tumor comprising nests and anastomosing islands of columnar cells within a fibrotic stroma. There is peripheral palisading of columnar cells with subnuclear vacuoles and reverse nuclear polarity. The center of the nests contain stellate reticulum-like cells with frequent cyst formation. Significant nuclear atypia, mitoses and necrosis are not seen. Perineural invasion is not identified. The tumor is 0.9mm from the resection margin. The remaining lymph node is unremarkable.

DIAGNOSIS: Left soft tissue ameloblastoma: Metastatic ameloblastoma within 1 of 2 lymph nodes; resection margins clear of tumor.

Ameloblastomas, previously known as an adamantinoma of the jaw, are benign, locally aggressive tumors that arise from the mandible, or less commonly from the maxilla. Usually presented as a hard painless lesion near the angle of the mandible in the 3rd to 5th decades of life. 

On imaging, they are commonly identified as a well-defined, expansive, and multiloculated ("soap bubble") lesion in the posterior mandible.

General imaging differential considerations include:

• dentigerous cyst: the relationship between ameloblastomas and dentigerous cysts is a controversial one, 20% of ameloblastomas thought to arise from pre-existing dentigerous cysts
• odontogenic keratocyst (OKC): usually unilocular with thin poorly enhancing walls
• odontogenic myxoma: can be almost indistinguishable
• aneurysmal bone cyst (ABC)
• fibrous dysplasia