ABSTRACT
<p><b>OBJECTIVE</b>To evaluate the expression of nuclear factor-kappaB (NF-kappaB), Ki-67 and matrix metalloproteinase-9 (MMP-9) in calcifying odontogenic cyst (COC), in order to investigate the proliferation and invasion of COC.</p><p><b>METHODS</b>Twenty-six cases of COC were classified into calcifying cystic odontogenic tumor (CCOT), dentinogenic ghost cell tumor (DGCT) and ghost cell odontogenic carcinoma (GCOC) based on the WHO classification of odontogenic tumors in 2005. The specimens of COC and 10 classic ameloblastoma (AB) were examined immunohistochemically to determine the expression of NF-kappaB p65, Ki-67 and MMP-9.</p><p><b>RESULTS</b>NF-kappaB was mainly detected in the cytoplasm of most tumor cells, but was only detected in the nucleus of few tumor cells (rate of nuclear staining < 1%). The expression of Ki-67 was significantly higher in GCOC than in CCOT (P < 0.001), DGCT (P < 0.05) and AB (P < 0.005). MMP-9 was detected both in tumor cells and stromal cells. GCOC showed significantly higher percentage of MMP-9 positive cases in stromal cells than CCOT, DGCT and AB (P < 0.05).</p><p><b>CONCLUSIONS</b>NF-kappaB may minimally affect the progression and invasion of COC. GCOC shows significantly higher proliferative activity and aggressiveness than CCOT and DGCT. MMP-9 in stroma may play a key role in the invasion of GCOC.</p>