Uterine smooth-muscle tumours: Practical approach to diagnosis

The diagnosis of uterine smooth-muscle tumours is generally unproblematic and straightforward. However, there are certain tumours that may create great challenges for the pathologist. The objective of this review is to highlight these difficulties and to make the approach to the diagnosis of smooth-muscle tumours more structured. For the purpose of this review, smooth-muscle tumours are divided into three major groups: (1) smooth-muscle tumours with clearly recognized smooth-muscle differentiation. These include benign, malignant and of uncertain malignant potential (STUMP). Within this group, variants such as mitotically active leiomyoma, cellular leiomyoma, symplastic (bizarre) leiomyoma, haemorrhagic cellular (apoplectic) leiomyoma, lipoleiomyoma, vascular leiomyoma and leiomyoma with haematopoietic elements are also included; (2) smooth-muscle tumours with no clearly recognized smooth-muscle differentiation such as myxoid, epithelioid, clear cell and granular cell leiomyomas as well as leiomyoma with sex cord-like pattern; (3) smooth-muscle tumours with unusual growth patterns such as diffuse uterine leiomyomatosis, intravenous leiomyomatosis, benign metastasizing leiomyoma, disseminated peritoneal leiomyomatosis, perinodular hydropic leiomyoma, multinodular hydropic leiomyoma, infiltrative uterine telomyoma and cotyledonoid dissecting leiomyoma or 'Sternberg tumour'. In this review, the pathological features of all these variants of smooth-muscle tumours are discussed and some unusual tumours are illustrated.