Salpingitis Isthmica Nodosa Salpingitis isthmica nodosa (SIN) is a noninﬂammatory pathologic condition of the tube in which tubal epithelium extends into the myosalpinx and forms a true diverticulum. The incidence in healthy controls is 6% to 11%, but this condition is found more often in the tubes of women with an ectopic pregnancy than in nonpregnant women (97). In one study, 46% of women with isthmic tubal pregnancy were found to have SIN (98). Myometrial electrical activity over the diverticula is abnormal. Whether tubal pregnancy is caused by SIN or whether the association is coincidental is unknown.
Endometriosis or Leiomyomas Endometriosis or leiomyomas can cause tubal obstruction. Neither is commonly associated with ectopic pregnancy.
Chorionic villi, usually found in the lumen, are pathognomic findings of tubal pregnancy (99). Gross or microscopic evidence of an embryo is seen in two-thirds of cases. An unruptured tubal pregnancy is characterized by irregular dilation of the tube, with a blue discoloration caused by hematosalpinx. The ectopic pregnancy may not be readily apparent. Bleeding associated with tubal pregnancies is mainly extraluminal but may be luminal (hematosalpinx) and may extrude from the fimbriated end. A hematoma is frequently seen surrounding the distal segment of the tube. Patients who have tubal pregnancies that spontaneously resolved and those treated with methotrexate frequently have an enlargement of the ectopic mass associated with blood clots and extrusion of tissue from the fimbriated end. Hemoperitoneum is nearly always present but is confined to the cul-de-sac unless tubal rupture occurred. The natural progression of tubal pregnancy is either expulsion from the fimbriated end (tubal abortion), involution of the conceptus, or rupture, usually around the eighth gestational week. Some tubal pregnancies form a chronic inﬂammatory mass that is associated with involution and reestablishment of menses and thus is difficult to diagnose. Extensive histologic sampling may be required to disclose a few ghost villi.
Histologic findings associated with tubal gestation include evidence of chronic salpingitis and SIN. Inﬂammation associated with salpingitis causes adhesions as a result of fibrin deposition. Healing and cellular organization lead to permanent scarring between folds of tissue. This scarring may allow transport of sperm but not the passage of the larger blastocyst. About 45% of patients with tubal pregnancies have pathologic evidence of prior salpingitis (56).
The cause of SIN is unknown but is speculated to be an adenomyosis-like process or, less likely, inﬂammation (100). This condition is rare before puberty, indicating a noncongenital origin. Tubal diverticula are identified in about one-half of patients who have ectopic pregnancies, as opposed to 5% of women who do not have ectopic pregnancies (101).
Histologic findings include the Arias-Sella reaction, which is characterized by localized hyperplasia of endometrial glands that are hypersecretory. The cells have enlarged nuclei that are hyperchromatic and irregular (102). The Arias-Sella reaction is a nonspecific finding that can be seen in patients with intrauterine pregnancies (Fig. 20.3).
Figure 20.3 The Arias-Stella reaction of the endometrium. The glands are closely packed and hypersecretory with large, hyperchromatic nuclei suggesting malignancy.