Atypical uterine leiomyoma: a case report and review of the literature

Atypical uterine leiomyomas show benign behavior. However, the distinction between leiomyomas and leiomyosarcomas may at times be problematic. We report a rare case of atypical uterine leiomyoma. We try to investigate potential immunohistochemical parameters that could be essential to distinguish cases of malignant smooth muscle tumors and those of uncertain or borderline histology.

A 56-year-old white ethnic Albanian woman from Kosovo presented with uterine bleeding because of uterine multiple leiomyomas. A hysterectomy with unilateral adnexectomy was performed. Her hysterectomy specimen contained multiple leiomyomas in submucosal, intramural and subserosal locations. The leiomyomas were well demarcated, firm and white with a whorled cut surface and one had foci of hemorrhage. Histology of most of the leiomyomas showed a whorled (fascicular) pattern of smooth muscle bundles separated by well-vascularized connective tissue. Smooth muscle cells were elongated with eosinophilic or occasional fibrillar cytoplasm and distinct cell membranes. Some of them developed areas of degeneration including hyaline change, with less than five mitotic figures per ten high power fields in most mitotically active areas, and no significant atypia. One leiomyoma was characterized by moderately to severely pleomorphic atypical tumor cells with low mitotic counts and no coagulative tumor cell necrosis. Immunohistochemistry showed strong immunoreactivity for vimentin, smooth muscle actin and desmin, while cyclin-dependent kinase inhibitor 2A (p16), and B-cell lymphoma 2 (bcl-2) showed focal immunoreactivity, estrogen and progesterone were positive, Ki-67 expressed a low proliferation index, whereas p21 and tumor suppressor gene p53 were negative.

The combination of evaluation of conventional morphologic criteria with cyclin-dependent kinase inhibitor 2A (p16), p21, progesterone, B-cell lymphoma 2, tumor suppressor gene p53 and Ki-67 expression may be of great value in the assessment of uterine smooth muscle tumors of uncertain or borderline histology.