Calretinin expression in ameloblastomas

Calretinin is a 29-kDa calcium-binding protein which is expressed in the central and peripheral nervous systems as well as in many other normal and pathological human tissues. The objective of this study was to determine whether calretinin was expressed in the epithelium of ameloblastomas.

Twenty-seven cases of unicystic ameloblastoma and 31 cases of solid and multicystic ameloblastoma were studied. Five-micron sections were immunohistochemically stained using either antiserum 7696 from Swant, or antiserum 18-0211 from Zymed with a standard ABC method. The results were identical with the two antisera. Positive staining was seen in 22 cases (81.5%) of unicystic ameloblastomas. This generally consisted of diffuse, intense nuclear and cytoplasmic staining of several cell layers of the more superficial cells both in the characteristic and nondescript areas of the cyst linings. In the solid and multicystic ameloblastomas, staining occurred in 29 (93. 5%) of the cases. The staining was almost always restricted to the stellate reticulum-like epithelium, was generally intense and diffuse in distribution. Areas of squamous metaplasia stained particularly intensely as did the cells surrounding micro- and macro-cysts. In both groups of lesions, most of the cases that did not stain were intensely inflamed.

The biological significance of calretinin expression in ameloblastomas is not known and its use as a distinctive, specific immunohistochemical marker for ameloblastic tissues remains to be confirmed. However, the results of this study raise the possibility that calretinin may be an important diagnostic aid in the differential diagnosis of cystic and solid ameloblastic tumours.