That's a basaloid epithelial tumor with stromal desmoplasia and ossification. I favor a desmoplastic ameloblastoma. The bland morphology and the lack of mitotic figures in the epithelial tumor component are in my view not well compatible with a carcinoma or a malignant ameloblastoma.

[comment sent by email on Sun, 25 Mar 2012 22:32:53 +0530]
I too thought it was an ameloblastoma, but the calcified foci suggest that  
an odonto-ameloblastoma /ameloblastic odontoma needs to be considered. What  
was the Xray picture?  
 

In my opinion, an odontogenic tumor can be ruled out. The lesion does not feature any of the characteristics of an ameloblastoma (peripheral palisading with subnuclear vacuoles, central reticulation resembling Str. intermedium of the enamal organ, broad collagenous band surrounding epithelial proliferations) or an odontoma (few calcifications aren´t enough). Furthermore, an ameloblastoma does not feature mineralized areas. An odontoameloblastoma is exceedingly rare and requires the combination of an ameloblastoma and an odontoma (which are both not present). It would be very important to know where exactly the lesion is located (intra-/extraosseous?? XRay?). If the tumor is located in the soft tissues a salivary gland tumor should be considered. The pictures suggest rather a benign tumor, but infiltrative growth can be focal and need to be ruled out. Anyway, the tumor should be completely excised.