Uterus, Leiomyosarcoma

Leiomyosarcomas of the uterus are uncommon malignancies of uterine smooth muscle, representing approximately 45% of uterine sarcomas. Their peak incidence is in patients in their 4th and 5th decades of age.

The histologic features shown are of a uterine mass composed of highly atypical neoplastic spindle cells. There is evidence of fascicular growth, tumour necrosis, and abundant mitoses. This case is remarkable for the presence of numerous osteoclast-like giant cells. Smooth muscle differentiation was demonstrated by immunohistochemistry (slides not provided), with tumour cells having reactivity for smooth muscle actin, and caldesmon (patchy).