Ki-67 and matrix metalloproteinase-9 expression in the follicular cyst, keratocystic odontogenic tumor, and ameloblastoma

An immunohistochemical study using antibodies against Ki-67 protein was conducted, which characterized the proliferative activity of cells and matrix metalloproteinase-9 (MMP-9) in follicular cyst, variants of keratocystic odontogenic tumor (with a preponderance of hyperkeratosis and parakeratosis), and ameloblastoma. The marked proliferative activity of a parabasal cell layer (28.0±8.4%) was found in the keratocystic odontogenic tumor with a preponderance of parakeratosis; the proliferative activity of the peripheral layer of ameloblastoma cells was equal to 7.0±5.6%. The maximal matrix metalloproteinase-9 expression in the keratocystic odontogenic tumor with a predominance of hyperkeratosis was 1.1 ±0.9 conventional units (CU) and that in the ameloblastoma was 1.9±1.3 CU versus 0.4±0.5 CU in the follicular cyst, keratocystic odontogenic tumor with a preponderance of hyperkeratosis. The values of Ki-67 and MMP-9 expression allow one to distinguish benign odontogenic cysts and tumors (follicular cyst and keratocystic odontogenic tumor with a predominance of hyperkeratosis) and odontogenic tumors characterized by an aggressive clinical course (keratocystic odontogenic tumor with a preponderance of parakeratosis and ameloblastoma).