Adenoid cystic carcinoma with morphological diversities--report of a case and discussion of the morphologic and immunohistochemical features.

A case of adenoid cystic carcinoma (ACC) with polymorphous features and an unknown differential diagnosis was presented. It appeared, without any pain, in the right maxillary sinus of a 47 year-old man. A variety of histopathological patterns were found, including glandular, cribriform, tubular and solid ones. However, the typical features of ACC, such as cribriform pattern associated with pseudocyst and tubular formations were rather scarce. A single cell strand appearance, so-called "Indian file arrangement", and papillary cystic formation were also noted, which are often associated with polymorphous low-grade adenocarcinoma (PLGA). Immunohistochemistries of EMA, CEA and musclespecific actin showed also similar staining patterns to those of PLGA in some areas. Our case could not be regarded as PLGA; but this case with features of PLGA as well as those of ACC might suggest an entity of transitional type between ACC and PLGA.