Prolactin binding in minor salivary gland tumors

An immunohistochemical study of 15 minor salivary gland tumors was initiated to determine if prolactin binding occurred in these tissues. Eight benign mixed tumors (BMT) and 7 adenoid cystic carcinomas (ACC) were selected at random from the surgical biopsy service of the MCV/VCU School of Dentistry, Department of Oral Pathology. The specimens were cut and mounted on slides along with sections of rat pituitary and rat ventral prostate which served as methodologic controls. Experimental specimens were incubated for 24 hours with varying concentrations of highly purified (iodination grade) rat prolactin; controls were incubated with vehicle. Following incubation the specimens were stained according to the Sternberger peroxidase-antiperoxidase method. Results showed dose-dependent staining for prolactin binding sites in 7 of 8 BMTs and 5 of 7 ACCs. The staining was wider in distribution than we observed in normal human minor salivary gland tissue. Binding was confined primarily to cells of duct origin in both types of tumor. In individual cells, staining was observed in diffuse cytoplasmic and perinuclear locations as well as in nuclei and apical regions. We conclude that two minor salivary gland neoplasms (BMT and ACC) exhibit prolactin binding at different cellular locations and in a more widespread pattern than was observed in normal minor salivary gland.