Uterine leiomyosarcoma arising in leiomyoma: clinicopathological study of four cases and literature review.

In this study we examined four cases of leiomyosarcoma (LMS) arising in leiomyoma (LM). The patients ranged from 40 to 64 years old. Symptoms were unspecific and preoperative diagnosis of LMS had not been made. Size of the tumors ranged from 4 cm to 20.5 cm. All patients were in stage I and no patients developed recurrent disease. Histologically, the LMS component showed moderate to severe cytological atypia and an increased mitotic count in all cases. Tumor cell necrosis in the LMS was seen in three cases. Associated LM component was cellular in one case. The LMS component showed p53 expression in three of four cases and p16 expression was seen in two cases. The LM component lacked p53 expression in all cases and demonstrated p16 expression in two cases, including one case of cellular LM. In all cases, Ki-67-positive cells were less than 5% in the LM component and more than 25-30% in the LMS component. This study reveals that: (i) malignant transformation can occur even in relatively small LM; (ii) patients with LMS with an LM component have a favorable prognosis; and (iii) immunohistochemical examination of p53, p16 and Ki-67 is useful for identification of malignant focus.