The aim of the current study is to evaluate the immunohistochemical expression of Ki-67; NCAM (neural cell adhesion molecule) also called CD-56, Cyclin-D1 and E-Cadherin in PAs and to study the possible association of the expression of these markers with the clinical manifestation of PAs, their tumor size and invasiveness as well as with the risk of recurrence. The gene discussed is MKI67; the disease is neoplasm.