MIB1 as a possible predictor of recurrence in low-grade endometrial stromal sarcoma of the uterus.

Objective: Immunohistochemical analysis of MIB1, p53, estrogen, and progesterone receptors can provide prognostic information in endometrial adenocarcinoma. Since predictors of recurrence for low-grade endometrial stromal sarcoma (LESS) are still unknown, a battery of immunostains was performed to find markers, which might be useful to predict prognosis.

Methods: Eleven patients with an average age of 43.8 years (range 27-76) were identified with stage I LESS. Immunostains, including MIB1, p53, ER, and PR, were evaluated by two pathologists, independently.

Results: All tumors were positive for ER and PR; 1/11 was positive for p53; MIB1 ranged from 0 to 20% positive tumor nuclei. Mitotic counts ranged from 0 to 7/10 hpf. Two patients developed recurrences. One had a pelvic recurrence 7 years after diagnosis. This tumor had a mitotic count of 1/10 hpf, MIB1 expression in 10% of nuclei, and focal p53 expression. A second patient developed pulmonary metastases 10.8 years after diagnosis; the tumor showed a mitotic count of 7/10 hpf and MIB1 expression in 20% of nuclei, but was negative for p53. There was a significant difference in MIB1 reactivity scores between patients who did or did not develop recurrence (P = 0.0303). A marginally significant association was detected between MIB1 (P = 0.0896) or p53 (P = 0.0833) positivity and length of recurrence-free survival.

Conclusion: Although MIB1 and p53 appear to be useful prognostic markers, a larger study would be necessary to confirm their validity.