ASSESSMENT OF PROLIFERATIVE ACTIVITY USING THE MIB1 ANTIBODY HELPS TODISTINGUISH POLYMORPHOUS LOW-GRADE ADENOCARCINOMA FROM ADENOID CYSTICCARCINOMA OF SALIVARY-GLANDS

Salivary polymorphous low grade adenocarcinoma (PLGA) and adenoid cyst ic carcinoma (AdCC) bear a superficial histological and immunophenotyp ic resemblance to each other, but can usually be separated by conventi onal microscopic examination. However, this is not always so, such as with PLGAs displaying plentiful cribriform structures, and when only l imited tissue from small biopsies is available for study. Twenty-one c ases of PLGA and 20 cases of AdCC from the surgical pathology files in Plzen, Exeter and Helsinki were incubated with the MIB1 antibody usin g the supersensitive avidin-biotin peroxidase technique after microwav e pretreatment. The antibody recognizes the cell cycle associated anti gen Ki-67 on routinely processed formalin-fixed paraffin-embedded tiss ues. The percentage of positively stained tumor cell nuclei constitute d the MIB1 index. It was found that the PLGAs had a mean MIB1 index of 2.4% (range 0.2-6.4), while the AdCCs had a mean value of 21.4% (rang e 11.3-56.7). Within the PLGA group, the 12 tumors which did not form micropapillae had a somewhat lower mean MIB1 index (1.4%) than those n ine in which such structures constituted a significant but minor compo nent (3.4%).