Adenoid cystic carcinoma: significance of DNA ploidy.

BACKGROUND

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.

METHODS

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.

RESULTS

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).

CONCLUSIONS

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.