MIB-1 (Ki-67), estrogen receptor, progesterone receptor, and p53 expression in atypical cells in uterine symplastic leiomyomas.

Nine cases of symplastic uterine leiomyomas were chosen from our files using strict criteria. An immunochemical study of the expressions of Ki-67, estrogen receptor, progesterone receptor, and p53 was performed. For each antigen, the percentages of positive atypical (bizarre) cells and nonatypical cells were compared. Both groups had identical and fairly high estrogen receptor and progesterone receptor immunohistochemical profiles and very low levels of p53 expression. The atypical cells had significantly higher percentages of cells expressing Ki-67 compared with nonatypical cells (17+/-20% vs. 3+/-3.9%). Therefore, rather than being degenerative in nature, the atypical cells are actively proliferating.