In this paper, we present a case of myxoid leiomyosarcoma development in a patient receiving tamoxifen for 3 years because of breast cancer. The myxoid leiomyosarcoma should be included in the differential diagnosis of any uterine tumor with a predominantly myxomatous composition. A review of the literature indicates that tamoxifen may increase not only the risk for endometrial cancer but also for uterine sarcoma, suggesting vigilance for uterine cancer in women who are being treated with this drug.

Massive lymphocytic infiltration of the leiomyomas of the uterus is rare and causes diagnostic difficulties. The objective of this study is to estimate the frequency, to analyze the clinicopathologic features, to explore the possible pathogenetic factors, and to discuss the differential diagnosis of this entity. We reviewed the pathology reports of 379 patients who underwent surgery for leiomyomas at our institution, from 1999 until 2003, and we identified five cases of leiomyomas with massive lymphocytic infiltration. Thereafter, we reviewed the records of these five patients to identify the clinical, ultrasonographic, and surgical findings they had presented. Leiomyomas with lymphocytic infiltration were characterized by the presence of small lymphocytes, few plasma cells, and occasional germinal lymphocytes such as lymphoblasts confined into the leiomyoma. Immunohistochemistry was positive for desmin and leukocyte common antigen and showed a positive reaction to kappa and lambda light chains that is consistent with the polyclonal nature of an inflammatory infiltration. Gross appearance and ultrasonographic and color Doppler findings were the same as of a typical leiomyoma. Lymphocytic infiltration of leiomyomas is a rare histological entity. Although an inflammatory process seems to be the pathogenetic factor, other mechanisms such as an immunological or autoimmune response, a specific human leukocyte antigen alteration, or a viral infection could also be the cause of this entity. Differential diagnosis must be made from malignant lymphoma, pyomyoma, and inflammatory pseudotumor of the uterus, based on their special histological characteristics.