Unilateral aneuploid dedifferentiated acinic cell carcinoma associated with bilateral-low grade diploid acinic cell carcinoma of the parotid gland.

A dedifferentiated acinic cell carcinoma (AciCC) of the right parotid gland with lymph node metastases occurred in a 36-year-old woman. The tumour was associated with a bilateral well-differentiated AciCC. The two components of this tumour had different (high and low) proliferative activity measured by Mib-1 and different (aneuploid and diploid) DNA content. Despite the presence of a high-grade component, TP53 mutations, microsatellite instability (MSI) and/or loss of heterozygosity (LOH) at the p53 locus were not detected. Although the follow-up of the patient is very short, the aggressiveness of the tumour is shown by a recurrence in the right parotid within 4 months and by the rapid development of regional metastases.