Purpose: To define the normal cut off of endometrial thickness as measured at transvaginal ultrasonography (TVUS) in order to define postmenopausal women without symptoms or with abnormal uterine bleeding (AUB) at risk of endometrial carcinoma (EC).
Materials and methods: 3460 postmenopausal women (2240 asymptomatic, 1220 with AUB) undergoing TVUS. These series was linked with the Tuscany Cancer Registry archives in order to identify subjects who developed EC subsequent (within two years) to TVUS.
Results: Thickness (half layer) was significantly reduced in 2234 subjects not developing EC (1.68 mm; range = 0-20, SD 3.14) as compared to 6 subjects developing EC (4.67 mm, range = 0-10, SD 3.67) (p=0.02). A 4 mm cut off was associated with a sensitivity of 66.7%, a specificity of 92.1%, a positive predictive value of 2.2% and a negative predictive value of 99.9%. Similarly, in subjects with AUB, thickness (half layer) was significantly smaller in the 1175 subjects not developing EC (2.46 mm, range 0-20, SD 3.59) as compared to 45 subjects developing EC (8.0 mm, range 0-44, SD 6.76) (p<0.001). The best cut off for clinical purposes was 4 mm, with a sensitivity of 91.1%, a specificity of 79.8%, a positive predictive value of 14.8% and a negative predictive value of 99.6%.
Conclusions: The study confirms the usefulness of measuring endometrial thickness (half layer cut off = 4 mm) with TVUS in asymptomatic postmenopausal women, both in asymptomatic subjects to indicate further special surveillance and in subjects with AUB to indicate immediate invasive assessment.