1. Human chorionic gonadotropin level as a predictor of trophoblastic infiltration into the tubal wall in ectopic pregnancy: a blinded study 
Andrea Natale, M.D., Massimo Candiani, M.D., Daniela Merlo, M.D., Stefano Izzo, M.D., Luciano Gruft, M.D., Mauro Busacca, M.D. 
Fertility and Sterility 
Volume 79, Issue 4, Pages (April 2003)
DOI: /S (02)

2. FIGURE 1
Classification of histologic findings in tubal samples into three stages, according to the depth of infiltration of the trophoblastic tissue. (A), In stage I the trophoblast is limited to the lumen or infiltrates the tubal mucosa. Tubal mucosa is well preserved, and trophoblastic columns are anchored at the tip of the plicae. (B), In stage II the trophoblast extends to the tubal muscularis. The lumen is dilated by blood, tubal mucosa is severely damaged, and anchoring villi penetrate into the muscolar wall. (C), In stage III the tubal wall is completely infiltrated and the serosa is made discontinuous by trophoblastic cells. Villi attain the serosal surface throughout tubal wall.
Natale. hCG and tubal infiltration in EP. Fertil Steril 2003.
Fertility and Sterility  , DOI: ( /S (02) )

3. FIGURE 2
(A), Relationship between gestational age and stage of trophoblastic infiltration of the tubal wall in ectopic ampullary pregnancy. The line represents the median. (B), Relationship between ultrasonographic diameter of tubal mass and stage of trophoblastic infiltration of the tubal wall. The line represents the median.
Natale. hCG and tubal infiltration in EP. Fertil Steril 2003.
Fertility and Sterility  , DOI: ( /S (02) )

4. FIGURE 3
Relationship between preoperative serum hCG level and stage of trophoblastic infiltration of the tubal wall in ectopic pregnancy. The line represents the median. Differences in hCG levels among groups were significant (P=.004,Kruskal–Wallis test).
Natale. hCG and tubal infiltration in EP. Fertil Steril 2003.
Fertility and Sterility  , DOI: ( /S (02) )