[A clinicopathological study of bizarre leiomyoma]

To investigate the feature of histomorphology and biology of uterine bizarre leiomyoma from the clinical, pathological features as well as the immunohistochemical expression.

Totally 25 cases of leiomyomas were studied. Among them, immuno-histochemical staining (SP and ABC methods) for smooth muscle actin (SMA), proliferative cell nucleus antigen (PCNA), estrogen receptors (ER), and progesterone receptors (PR) were performed in 20 cases. The clinical features and follow-up records were analyzed.

The main clinical findings were irregular vaginal bleeding, pain and pelvic tumor. One case was with immense amount of ascitis and the other two were with pregnancy. All the cases had no history of taking pregestine. Light microscopy showed that part of all the cell nuclei were bizarre, accompanying with double or multiple nuclei in which rather big and reddish staining inclusion bodies were obtained (D = 7 - 26 micro m), and the mitotic figures were 0 - 2/10 HPF. Among 20 cases with immunohistochemical staining, markers indicating muscle cells in origin were positive in the bizarre cells, 15 of which (75%) with negative or weak positive PCNA, and 18 of which (90%) with negative ER. There were significant difference between the studied and control groups (P = 0.027, P < 0.005 respectively) and in addition, PR was positive in both these two groups. A majority of the nucleus inclusion bodies was SMA positive. Follow-up records demonstrated so far no recurrence cases obtained.

Uterine atypical leiomyoma belongs to benign tumor, although its shape is bizarre. In this group, the morphology changes are correlated with pregnancy, but not with pregestine. The expression of immunohistochemistry shows certain features, and is important to identify uterine bizarre leiomyoma with leiomyosarcoma and STUMP in pathological diagnosis.