Immunohistochemistry (Ki-67 and p53) as a tool in determining malignancy in smooth muscle neoplasms (exemplified by a myxoid leiomyosarcoma of the uterus).

Smooth muscle tumours of the uterus at times represent a problem as it may be difficult to distinguish between benign and malignant tumours. The myxoid leiomyosarcoma (a rare type of neoplasm) reported here is an example of this. We present a case history and examine the suitability of Ki-67 and p53 as indicators of malignancy. The two antibodies were tested on seven leiomyomas, three atypical (borderline) leiomyomas, seven leiomyosarcomas and the myxoid leiomyosarcoma using microwave oven antigen retrieval. The leiomyomas had the lowest and the leiomyosarcomas the highest proliferation rate. The leiomyomas had no expression of p53, the atypical leiomyomas had a few scattered positive nuclei, and 5/7 of the leiomyosarcomas had overexpression of p53. The myxoid leiomyosarcoma had a positive reaction for p53 in clusters. The results suggest that Ki-67 and p53 might be useful as indicators of malignancy.