28 September 2006 Case of the Week #60
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We thank Dr. Jamie Shutter, George Washington University, Washington, D.C. (USA) for contributing this case. This case was reviewed in May 2020 by Dr. Jennifer Bennett, University of Chicago and Dr. Carlos Parra-Herran, University of Toronto.
Case of the Week #60
A 45 year old woman had menometrorrhagia (irregular or excessive bleeding during menstruation and between menstrual cycles), and had an endometrial biopsy.
What is your diagnosis?
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Endometrial intraepithelial neoplasia (EIN)
This case was sent as an example of the relatively new classification system (see Gynecol Oncol 2000;76:287) for a precursor to endometrioid endometrial adenocarcinoma, as an alternative to the World Health Organization system of complex or simple hyperplasia with or without atypia. Under WHO, this case would likely be classified as complex hyperplasia with atypia. A comprehensive website dedicated to the EIN classification system is www.endometrium.org.
Using the definition of EIN, most cases are monoclonal and thus premalignant, in contrast to endometrial hyperplasia, which may or may not be monoclonal or premalignant. The criteria for EIN includes:
(a) a larger glandular area than stromal area (volume percent stroma < 55%)
(b) cytology differs between the crowded glandular focus and the background glands
(c) the premalignant area is at least 1 mm
In addition, one must exclude progesterone related effects (wait 2-4 weeks after cessation of hormones), benign mimics (disordered proliferative endometrium or atrophy) and carcinoma.
A recent study found that the EIN system predicts disease progression more accurately than the WHO system (Cancer 2005;103:2304). Another study showed high levels of agreement between pathologists on the presence or absence of EIN and suggested that EIN better classifies patients into high and low risk subgroups (Mod Pathol 2005;18:324)
This new classification system has not been adopted into the latest versions of two popular general surgical pathology textbooks (Mills: Sternberg's Diagnostic Surgical Pathology 2004, Rosai: Rosai and Ackerman's Surgical Pathology 2004).
Additional references: J Clin Pathol 2002;55:326
Nat Pernick, M.D., President
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