Purpose:
Overlapping clinicopathological and immunopathological features of polymorphous low-grade adenocarcinoma (PLGA) and adenoid cystic carcinoma (ACC) may present a diagnostic problem, particularly with respect to small tissue biopsies from intraoral lesions. The aim of this study was to compare expression of Bcl-2, MIB-1 and TP53 in PLGA and ACC.

Materials and Methods:
Ten PLGA, 11 ACC and 19 normal salivary gland controls were stained with antibodies Bcl-2, MIB-1and TP53. Bcl-2 and TP53 immunostaining was subjectively assessed using semi-quantitative methods previously described in the literature, while a novel objective approach using a digital imaging system was used to assess MIB-1 staining.

Results:
There was increased expression of TP53, Bcl-2 and Ki-67 (MIB-1) in ACC, although the differences were ificant. However, MIB-1 was significantly increased in the solid pattern of ACC.

Conclusions:
MIB-1 staining may be of value in discriminating between more and less aggressive tumours. Further study of larger series is needed to elucidate differences between PLGA and ACC.

Key words:
polymorphous low-grade adenocarcinoma, adenoid cystic carcinoma, MIB-1, Bcl-2, TP53