Tumour growth fraction and apoptosis in salivary gland acinic cell carcinomas. Prognostic implications of Ki-67 and bcl-2 expression and of in situ end labelling (TUNEL).

bcl-2 protein and Ki-67 (MIB-1) were studied in 32 acinic cell carcinomas (ACCs), all with a minimum of 5 years' clinical follow-up. Tumour apoptosis was evaluated by TdT dUTP nick end labelling (TUNEL) and by morphological criteria. Five patients died of their disease. Patients with stage I tumours had significantly better survival compared with other stages (P < 0.05). Patients with MIB-1-negative tumours had significantly better survival than patients with MIB-1-positive tumours (P = 0.05). This study confirms a previous report that MIB-1 is an independent prognostic factor for survival in patients with ACC. Stage I tumours had high expression of bcl-2 protein, but there was no difference when compared with other stages. TUNEL positivity was most prevalent in stage I tumours, compared with stages II, III, and IV (P < 0.05), probably indicating more apoptosis. This could imply a capacity of stage I tumours ('early tumours') for early selection of tumour cells for elimination by apoptosis. There was no significant difference between expression of bcl-2 and TUNEL, between these parameters and clinical outcome, or between any parameter and morphological subclassification. We conclude that MIB-1 has prognostic value in ACC. Clinical staging, bcl-2, and TUNEL are also potentially useful as prognostic markers.