Leiomyosarcoma of the rectum. A report of two cases and review of the literature.

Rectal leiomyosarcoma is rare. It is frequently treated by abdominoperineal resection. The role of adjuvant therapy is unclear. Two cases of rectal leiomyosarcoma are presented. Pre-operative endorectal ultrasound predicted submucosal invasion in one case treated by low restorative resection and muscularis propria infiltration in the other managed with abdominoperineal resection. In both cases, ultrasound suggested malignant characteristics as evident by heterogeneous cystic spaces, irregular outline, large size and echogenic foci. Histology was CD34 negative and desmin, alpha-smooth muscle actin and HHF-35 positive, distinguishing these tumours from gastrointestinal stromal tumours. Rectal leiomyosarcoma may be successfully treated by restorative resection and pre-operative ultrasound is useful in assisting this surgical decision by defining malignant features of the tumour. Histopathological characteristics predictive of poor prognosis include high mitotic activity, intratumoural necrosis and tumour size.