**2. Overview**

The lifetime risk of a woman in the United States to develop uterine cancer is 2.5%. It is the fourth most common cancer in women and accounts for 6% of all female cancers and 3% of cancer-related deaths (Jemal et al., 2010). Two different clinico-pathological subtypes of endometrial cancer are recognized: Type I, which is endometrioid and estrogen-related, and Type II, which is non-endometrioid and non-estrogen-related.

When the disease is confined to the uterus, a hysterectomy and bilateral salpingooophorectomy would constitute adequate treatment. If the disease has spread outside the uterus, adjuvant treatment is required to maximize the potential for cure. At the time of diagnosis approximately 85% of endometrioid cancers are confined to the uterine corpus and are therefore associated with a favorable five-year survival rate of 83% (Creasman et al., 2006). In the Western world at least 85% of newly diagnosed endometrial cancers are endometrioid in type (Amant et al., 2005; Creasman et al., 2006). As the propensity for lymph node metastasis in these patients can vary from clinically negligible to 20%, depending on the grade and stage of presentation, management of this subtype is fraught with ambiguity. In non-endometrioid cancers, 35% have already spread beyond the uterine corpus at presentation. Among the non-endometrioid uterine cancers, clear cell and papillary serous cancers are the worst offenders, with extra-uterine metastasis occurring in 33% and 41% of cases, respectively, which is reflected in correspondingly low five-year survival rates of 63% and 53%, respectively (Creasman et al., 2006).

Following primary surgical treatment, adjuvant treatment is tailored according to the risk of lymph node metastasis and recurrent disease. The current method of risk stratification uses patient-related factors as well as the definitive pathological findings identified to be associated with increased risk of lymph node metastasis and recurrence to group patients into low-, intermediate- and high-risk categories. Other determinate factors are age, tumor grade, non-endometrioid subtype and extension of the disease, including depth of myometrial invasion and lymphovascular space invasion (LVSI) (Creasman et al., 1987; Kadar et al., 1992; Keys et al., 2004; Morrow et al., 1991).


Table 1. Classification of endometrial cancers adjusted to FIGO 2009.

The disadvantage of this system is that lymph node metastasis is presumed rather than known for certain, and a proportion of patients will be over-treated with adjuvant treatment. Furthermore, if removal of the affected nodes has a therapeutic value, and evidence suggests it has (please refer to section 6), patients would miss out on the survival advantage conferred by a systematic lymphadenectomy. Having access to information about lymph node status pre-operatively would allow surgery to be tailored accordingly. Below, we discuss the currently available methods for pre-operative assessment of the spread of disease.
