Fetal endometriosis A case report

A fetal pelvic mass was diagnosed at 35 weeks’ gestation and removed on day of life 2, revealing endometriosis. This case provides some support for theories on the pathophysiology of neonatal endometriosis.

Meike Schuster, D.O., Dhanya Mackeen, M.D., M.P.H.

Volume 103, Issue 1, Pages 160-162


To report a case of a large fetal pelvic mass diagnosed at 35 weeks’ gestation.

Report of a unique case of a fetal abdominal mass, emphasizing the wide range of differential diagnoses. Although rare reports of fetal ovarian cysts exist, even fewer describe endometriosis or endometriomas in infants. As of 2014 there have not been any published reports of fetal endometriosis from the United States.

Large tertiary community hospital.

An 18-year-old pregnant woman diagnosed with a large fetal pelvic mass at 35 weeks’ gestation.

Diagnosis of a fetal abdominal mass at 35 weeks with documented enlargement at 37 weeks leading to delivery, with subsequent removal of the mass on day of life 2.

Main Outcome Measure(s):
On day of life 2, a pediatric surgeon performed an exploratory laparotomy and left salpingo-oophorectomy.

Final pathology showed a 7.0 × 4.5 cm cyst-like structure consistent with hemorrhagic ovarian cyst wall and focal endometriosis.

It can be very difficult to counsel patients regarding an abdominal mass in their unborn child. These difficulties stem from the large list of differential diagnoses and the range of prognoses they portend. As more and more of these cases appear in the literature, we are able to gain a better understanding of how each of these diagnoses present and appear on imaging, allowing us to provide a more accurate diagnosis and counseling antenatally.

  • Ronald E. Batt, MD

    endometriosis: acquired or embryonic?

    the Editor:

    We read with great interest
    the case of focal fetal-endometriosis in a live newborn reported by Schuster
    and Mackeen. (1) “Final pathology showed a translucent, thin-walled…cyst-like structure…with
    a 3.8 x 2.0 cm opaque portion of fibromembranous tissue and red-brown clot-like
    material…consistent with hemorrhagic ovarian cyst wall and focal
    endometriosis.” However, this description is insufficient; identification of
    ectopic endometrial glands and stroma is necessary to establish an unequivocal
    diagnosis of endometriosis.

    Two forms of fetal
    endometriosis have been identified: acquired-fetal endometriosis (2), explained
    by the theory of early-onset endometriosis (3, 4), and embryonic-fetal
    endometriosis (5), explained by the theory of müllerianosis. (6, 7) If the
    endometriosis arose from müllerian tissue misplaced during embryogenesis, then
    one should find an organoid structure (choristoma) composed of normal
    endometrial tissue misplaced within
    the ovary and the pathogenesis of the fetal-embryonic endometriosis explained
    by the theory of müllerianosis. (6, 7) If, on the other hand, the endometriosis
    resulted from retrograde shedding of fetal endometrial stem/progenitor cells,
    then one may expect the endometriotic lesion to be located on the surface of
    the ovary – with or without adhesions – and the pathogenesis explained by the
    theory of early-onset acquired endometriosis (3, 4).

    This distinction has
    consequences. Fetal-embryonic endometriosis, being a choristoma – i.e. a
    congenital anomaly – can be cured by excision.
    However, fetal-acquired endometriosis resulting from retrograde shedding
    of endometrial stem/progenitor cells may recur after excision.

    Ronald E. Batt, M.D.,

    Department of Obstetrics and Gynecology

    University at Buffalo, State University of New York

    Buffalo, New York

    John Yeh, M.D.

    Department of Obstetrics, Gynecology and Reproductive

    Massachusetts General Hospital

    Harvard Medical School

    Boston, Massachusetts


    1. Schuster
    M, Mackeen DA. Fetal endometriosis: a case report. Fertil Steril. 2015

    2. Arcellana
    RC, Robinson TW, Tyson RW, Joyce MR. Neonatal fellowship. McKusick-Kaufman
    syndrome with legal complications of hydrometrocolpos and congenital
    endometriosis. J Perinatol. 1996 Mah-June;16(3 Pt 1):220-3)

    3. Brosens
    I, Brosens J, Benagiano G. Neonatal uterine bleeding as antecedent of pelvic
    endometriosis. Hum Reprod. 2013 Nov;28(11):2893-7.

    4. Gargett
    CE, Schwab KE, Brosens JJ, Puttemans P, Benagiano G, Brosens I. Potential role
    of endometrial stem/progenitor cells in the pathogenesis of early-onset
    endometriosis. Mol Hum Reprod. 2014 Jul;20(7):591-8.

    5. Signorile
    PG, Baldi F, Bussani R, D’Armiento M, De Falco M, Baldi A. Ectopic endometrium
    in human fetuses is a common event and sustains the theory of müllerianosis in
    the pathogenesis of endometriosis, a disease that predisposes to cancer. J Exp
    Clin Cancer Res. 2009 Apr 9;28:49.

    6. Batt
    RE, Smith RA, Buck Louis GM, Martin DC, Chapron C, Koninckx PR, Yeh J.
    Müllerianosis. Histol Histopathol. 2007 Oct;22(10):1161-6.

    7. Batt
    RE, Yeh J. Müllerianosis: four developmental (embryonic) müllerian diseases.
    Reprod Sci. 2013 Sep;20(9):1030-7.

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