OBJECTIVE: Parathyroid hormone-related protein (PTHrP) production has been 
demonstrated in a variety of tumor subtypes. Local production of PTHrP by 
metastatic tumor cells in bone has been linked to bone destruction and tumor 
growth. Ameloblastoma (AB) is a relatively common odontogenic epithelial 
neoplasm that manifests local infiltrative intraosseous growth. AB recapitulates 
the developing enamel epithelium, in which PTHrP recently has been demonstrated. 
Yet PTHrP expression in a series of ABs has not been studied to date. The 
purpose of this investigation is to assess the expression of PTHrP in 
ameloblastoma.
STUDY DESIGN: Formalin-fixed, paraffin-embedded tissue sections of ameloblastoma 
(n = 30; 24 conventional, 4 unicystic, and 2 arising in dentigerous cyst) were 
immunostained with anti-PTHrP antibody using a multistep streptavidin-peroxidase 
technique. Semiquantitative scoring of immunoreactivity was assessed as mild, 
moderate, and intense.
RESULTS: All cases (100%) demonstrated positive immunoreactivity, with mild 
reaction in 3 conventional ABs, 1 unicystic and 1 AB arising in dentigerous 
cyst, and with moderate reaction in 12 conventional ABs, 3 unicystic and 1 AB 
arising in dentigerous cyst. Intense immunoreactivity was seen in 9 cases of 
conventional AB. This difference in immunostaining was not statistically 
significant (Sigma2 = 4.41, df = 4, P = .358).
CONCLUSION: The results of this investigation suggest that PTHrP may play a 
significant role in local bone resorption, offering at least partial explanation 
for the tumor's infiltrative growth and destructive behavior. The uniformity of 
PTHrP expression by AB, as detailed in this study, may harbor significant 
therapeutic implications, particularly through PTHrP-blocking treatment 
modalities.