Adenoid cystic carcinoma: significance of DNA ploidy

DNA ploidy pattern is sometimes used as a prognostic factor. Heterogeneity of a tumor could, however, give false information when a single analysis is performed.

Twenty-eight patients with adenoid cystic carcinomas were retrospectively studied with regard to clinico-histologic parameters, and in 24 of these the DNA pattern was assessed using flow cytometry, with multiple analysis from different tumor parts, to determine prognostic factors.

Of the carcinomas, 33% (8/24) were DNA aneuploid, and 17% (4/24) of the tumors showed intratumoral heterogeneity of DNA content; two of them with mixture of diploid and aneuploid stemlines. The DNA aneuploid tumors were clinically more advanced and demonstrated a higher frequency of solid architecture than did diploid tumors (p < 0.05). The S-phase values were significantly higher in aneuploid samples than in diploid ones (p < 0.05). The recurrence rate was significantly higher in patients with aneuploid tumors (75%) than with diploid ones (19%) (p < 0.05). The cumulative survival was worse for patients with aneuploid tumors than for those with diploid ones (p < 0.05).

Our findings suggest a potentially important role for flow cytometry in evaluation of adenoid cystic carcinoma. It is of interest to observe that in some tumors both diploid and aneuploid stemlines can co-exist. If one sample is analyzed and demonstrates diploid cells, there is a 3% chance that the tumor is also heterogeneous with aneuploid stemlines. If one sample demonstrates aneuploid cells, there is a 7% chance for heterogeneity with diploid cells, as well. Two samples from different tumor parts can be considered representative.