Answer: Pindborg tumor

Histology: The tumor is characterized by cords and nests of cuboidally-shaped epithelioid cells with round nuclei. The cytoplasm is granular and pink. The stroma adjacent to the tumor has a hyaline appearance, which is entirely consistent with amyloid. The presence of amyloid is easily confirmed with a Congo red stain. These are the characteristic features of the calcifying epithelial odontogenic tumor, also known as Pindborg tumor.

Discussion: Metastatic carcinoma would feature more pleomorphism, and would not demonstrate the amyloid formation seen in the current case. Ameloblastoma features islands of neoplastic ameloblasts, which demonstrates peripheral palisading of their nuclei and subnuclear vacuolization, surrounding stellate reticulum cells. A plasmacytoma might be associated with amyloid deposition, but the tumor cells would demonstrate clock-face type chromatin and eccentric cytoplasm.

The calcifying epithelial odontogenic tumor is a locally aggressive one, similar to ameloblastoma. Concentric calcification of the amyloid within the tumor leads to the Liesegang phenomenon in many cases.