Foreign body (alginate impression paste) in the maxillary sinus: a case report.

A tumor-like foreign body in the maxillary sinus is reported. Examination of the paranasal sinuses by computerized tomography revealed a dense and well defined lesion equal to that of bone in the left maxillary sinus. After surgery, the lesion was found to be alginate used for impression-taking before fitting of a prosthesis, and not a tumor.