Smooth Muscle Tumors of Uncertain Malignant Potential of Uterine Origin

Abstract

Smooth muscle tumors of uncertain malignant potential or otherwise known as the “STUMP” is a rare group of smooth muscle tumors intermediate between leiomyomas and leiomyosarcomas (LMS) [1] . The term “STUMP” was first used by Kempson in 1973 [2]. It was the work of Taylor and Norris which established the importance of mitotic figures in evaluating smooth muscle tumors of the uterus a half century ago [2], but it soon became evident that some uterine smooth muscle neoplasms with relatively low mitotic indices (5–10 mitotic figures [mf] per 10 high-power fields [hpf]) were capable of behaving in a clinically aggressive manner and that not all tumors with a mitotic index greater than 10 mf/10 hpf were clinically malignant. The term smooth muscle tumor of uncertain malignant potential was created for the 5–9 mitotic index group to reflect the uncertainty about the true failure rate in this group [3–7]. WHO defines STUMP as a smooth muscle tumor that cannot be diagnosed reliably as benign or malignant on the basis of generally applied criteria [8].