Fallopian tubes & broad ligament

• Salpingitis isthmica nodosa (SIN) is an outpouching of the fallopian tube epithelium into the smooth muscle wall (adenomyosis of the tube)
• Multiple discrete lumina are enveloped in smooth muscle and in severe cases, the tubal lumen may be completely obstructed
• SIN can lead to infertility or ectopic pregnancy

• Diverticulosis of the fallopian tube
• Tubal adenomyosis

• 0.6 - 11% of healthy fertile women (StatPearls: Salpingitis Isthmica Nodosa [Accessed 22 June 2023], Fertil Steril 1993;60:599)
• Incidence is ~1% in the white female population (Fertil Steril 1978;29:164)
• Primarily affects young women of reproductive age (mean: 26 years)
• 10% incidence in cases of ectopic tubular pregnancies (Gynecol Obstet Invest 1992;34:202)

• Unclear but early theories include inflammatory or congenital causes (Radiology 1985;154:597)
• Other controversial hypotheses include
  • Origination in Wolffian rests or mesonephric rests due to SIN occurring at the location in which these ducts cross during embryologic development (Clin Radiol 1987;38:207)
  • Acquired etiology with some studies suggesting diethylstilbestrol exposure; chronic tubal spasm due to increased intramural pressure / weakness in the wall at the site of vasculature (Clin Obstet Gynecol 1987;30:181)
  • Infectious etiology due to chronic infection or inflammation

• More common in the background of ectopic pregnancy and infertility
• Associated with infertility in 50% of patients but its presence may not actually affect the number of births (Hum Reprod 1991;6:828)
• Incidence in healthy, fertile women ranges from 0.6 to 11% (Fertil Steril 1993;60:599)
• May be unilateral or bilateral

• Incidental finding during evaluation for pelvic pain or infertility (hysterosalpingogram [HSG], laparotomy, laparoscopy)
• Tubal evaluation for primary infertility may reveal gross lesion
• HSG can demonstrate the nodular swellings (Fertil Steril 1993;60:599)
• No pathognomonic clinical symptomatology

• Hysterosalpingography (HSG)
  • Globular 2 mm diameter collections of contrast medium in isthmus
  • Tubal occlusion and hydrosalpinx may be observed

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• Firm, nodular swellings of the fallopian tube, ranging in size up to 2 cm in greatest dimension (Br J Radiol 2021;94:20201386)
• May be unilateral or bilateral
• Smooth, intact serosal covering
• Cross section of the nodules reveal gray, yellow or brown tissue punctuated by small cysts that surround the original tubal lumen (StatPearls: Salpingitis Isthmica Nodosa [Accessed 22 June 2023])
• Nodosity of the isthmus may give the uterus a horned appearance

AFIP images


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• Regularly spaced glands lined by normal appearing tubal epithelium surrounded by smooth muscle or fibrous tissue
• Tubal lumina are true diverticula that communicate with the central tubal lumen but do not connect with the serosa
• Glands can become cystically dilated (Am J Clin Pathol 1951;21:212)
• No significant atypia, scarring or associated inflammatory / stromal response
• Absence of endometrial stroma differentiates this entity from tubal endometriosis

Contributed by Jessica L. Bentz, M.D., AFIP and @Andrew_Fltv on Twitter

What is the most common clinical sequela associated with salpingitis isthmica nodosa?

1. Ectopic pregnancy
2. Endometrioid adenocarcinoma
3. Endometriosis
4. Fitz-Hugh-Curtis syndrome
5. Serous tubal intraepithelial carcinoma (STIC)

A. Ectopic pregnancy. The most commonly documented and reported clinical sequela of salpingitis isthmica nodosa (SIN) is ectopic pregnancy. Answers E and B are incorrect because SIN is not a premalignant or malignant lesion. Answer C is incorrect because endometriosis is not a known clinical consequence of SIN. Answer D is incorrect because Fitz-Hugh-Curtis syndrome results from pelvic inflammatory disease, which may be seen in patients with SIN.

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Reference: Salpingitis isthmica nodosa

A 48 year old woman with a history of infertility undergoes a hysterectomy with bilateral salpingectomy for abnormal uterine bleeding. What is the most likely diagnosis in her right fallopian tube?

1. Endometrioid adenocarcinoma
2. Endometriosis
3. Endosalpingiosis
4. Salpingitis isthmica nodosa (SIN)
5. Serous cystadenofibroma

D. Salpingitis isthmica nodosa (SIN). SIN is the correct answer with multiple cystically dilated glands in the muscular wall of the tube and is common in patients with a history of infertility. Answer A is incorrect because endometrioid adenocarcinoma will have nuclear atypia and glandular complexity. Answer B is incorrect because endometriosis may appear as dilated glands in the muscular wall but will contain surrounding endometrial stroma, differentiating this entity from SIN (which does not contain associated endometrial stroma). Answer C is incorrect because endosalpingiosis is usually found in the peritoneum. Answer E is incorrect because serous cystadenofibroma will be grossly described as a cystic mass lesion, more commonly found on the ovary.

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Reference: Salpingitis isthmica nodosa