Ovary nontumor
Nonneoplastic cysts / other
Epithelial inclusion cyst

Author: Aurelia Busca, M.D., Ph.D. (see Authors page)
Editor: Carlos Parra-Herran, M.D.

Revised: 19 September 2017, last major update September 2017

Copyright: (c) 2002-2017, PathologyOutlines.com, Inc.

PubMed Search: Epithelial inclusion cysts [title]

Cite this page: Busca, A. Epithelial inclusion cyst. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/ovarynontumorinclusioncyst.html. Accessed December 15th, 2017.
Definition / general
  • Invaginations of the ovarian surface epithelium into the ovarian cortex
Essential features
  • Two types based on morphology and pathophysiology:
    • Peritoneal inclusion cyst: lined by flat epithelium invaginated from ovarian surface epithelium; these express a peritoneal phenotype (calretinin, WT1 and D2-40 positive, PAX8 and BerEP4 negative)
    • Müllerian inclusion cyst: lined by ciliated tubal epithelium as a result of implantation of tubal epithelium in the ovarian parenchyma, presumably at the time of ovulation when the ovarian surface epithelium is disrupted; these express a tubal Müllerian phenotype (PAX8, BerEP4 and WT1 positive, calretinin and D2-40 negative)
  • Size is less than 1 cm; if more than 1 cm, by convention the lesion is designated as cystadenoma or cystadenofibroma
Terminology
  • Cortical inclusion cyst
Epidemiology
  • Can occur at any age but more common postmenopausal
Pathophysiology
Clinical features
  • Incidental findings, usually asymptomatic
Prognostic factors
  • Benign entities
  • Presence of inclusion cyst in postmenopausal women does not increase the risk of ovarian or other hormone driven cancers (breast and endometrial cancers, BJOG 2012;119:207)
  • Traditionally thought to represent a precursor lesion of ovarian carcinoma, but most ovarian serous carcinomas are now considered as tubal in origin with serous tubal intraepithelial carcinoma (STIC) as precursor lesion
  • For a subset of ovarian serous carcinomas in which STIC or tubal involvement is not identified, a potential origin in epithelial inclusion cyst of Müllerian (tubal) phenotype has been postulated (Gynecol Oncol 2013;130:246, Mod Pathol 2011;24:1488, Int J Gynecol Pathol 2015;34:3)
  • Use of oral contraceptives for more than 5 years was shown to reduce the number of Müllerian type inclusion cysts (PAX8 positive), supporting the hypothesis that this subtype constitutes a precursor lesion of ovarian serous carcinoma (Diagn Pathol 2016;11:30)
Gross description
  • Most are not apparent grossly unless very superficial in the cortex
  • When visible, they appear as small cysts bulging at the ovarian surface
Microscopic (histologic) description
  • Small cysts ( < 1 cm)
  • Peritoneal inclusion cyst: lined by simple flat epithelium devoid of cilia or mucinous cytoplasm
  • Müllerian inclusion cyst: lined by simple cuboidal to columnar epithelium with ciliated cells, sometimes admixed with nonciliated (secretory, peg) cells
  • Can have psammoma bodies in adjacent stroma
Microscopic (histologic) images

Images hosted on other servers:

Various images

Immunohistochemical images of the tumor

Immunohistochemistry
Differential diagnosis
  • Endometriosis: presence of endometrial stroma or hemosiderin laden macrophages
Board review question #1
Which of the following immunohistochemical markers is NOT useful in determining the phenotype of an ovarian epithelial inclusion cyst?

  1. BerEP4
  2. Calretinin
  3. D2-40
  4. ER
  5. PAX8
Board review answer #1
D. BerEP4 and PAX8 are positive in Müllerian type cysts, while D2-40 and calretinin are positive in peritoneal type inclusion cysts.