Flow cytometric evaluation of adenoid cystic carcinoma: correlation with histologic subtype and survival

Adenoid cystic carcinoma is an unusual but capricious tumor of salivary gland origin. Characteristically, these tumors follow a relentless clinical course, although some patients experience prolonged disease-free survival. Tumor size, site, and grade have been shown to correlate with tumor behavior. Recent investigation by others has suggested that DNA ploidy as determined by flow cytometry may provide an additional biologic marker of tumor behavior. This study was undertaken to investigate the relationship of DNA ploidy to tumor grade, biologic behavior, and patient outcome. A retrospective comparison of flow cytometric evaluations of paraffin-embedded formalin-fixed tumor specimens with patient outcome and histopathologic grade was undertaken. Follow-up of 4 to 7 years in 26 patients confirmed that the presence of a solid histologic component in the tumor correlated with the presence of recurrent or persistent disease (p = 0.04). Twenty-two of 28 tumors (78%) were found to be aneuploid on at least one section. Comparison of DNA ploidy with either patient outcome or the presence of a solid component did not achieve statistical significance, although a trend was suggested. This study confirms previous studies demonstrating the validity of histopathologic evaluation of tumor grade in the prediction of the biologic behavior of adenoid cystic carcinoma. However, our findings suggest that DNA ploidy has only limited value as an additional marker of tumor behavior in this patient population.