Ovary
Other nonneoplastic
Epithelial inclusion cyst
Topic Completed: 1 September 2017
Minor changes: 16 October 2020
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PubMed Search: Epithelial inclusion cysts [title]
Table of Contents
Definition / general | Essential features | Terminology | Epidemiology | Pathophysiology | Clinical features | Prognostic factors | Gross description | Microscopic (histologic) description | Microscopic (histologic) images | Immunohistochemistry | Differential diagnosis | Board review style question #1 | Board review style answer #1Cite this page: Busca A, Parra-Herran C. Epithelial inclusion cyst. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/ovarynontumorinclusioncyst.html. Accessed January 18th, 2021.
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
- Via invagination of the ovarian surface epithelium (peritoneal type cyst) or implantation of tubal epithelium when the ovarian surface epithelium is disrupted at ovulation (Müllerian type cyst, Int J Gynecol Pathol 2015;34:3, Mod Pathol 2011;24:1488)
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:
Figure 1:
immunophenotype
Figure 2:
ovarian surface
epithelia
Figure 3:
OEIs with double
PAX8 and
calretinin staining
Figure 4:
secretory cell
expansion
Immunohistochemical
images of the tumor
Immunohistochemistry
- Müllerian type cyst: PAX8, BerEP4 and WT1 positive, calretinin and D2-40 negative
- Peritoneal type cyst: calretinin, WT1 and D2-40 positive, PAX8 and BerEP4 negative (Int J Gynecol Pathol 2015;34:3)
- Presence of PAX8 in surface ovarian epithelium has been linked to neoplastic transformation (Hum Pathol 2015;46:948)
Differential diagnosis
- Endometriosis: presence of endometrial stroma or hemosiderin laden macrophages
Board review style question #1
Which of the following immunohistochemical markers is NOT useful in determining the phenotype of an ovarian epithelial inclusion cyst?
- BerEP4
- Calretinin
- D2-40
- ER
- PAX8
Board review style answer #1
D. BerEP4 and PAX8 are positive in Müllerian type cysts, while D2-40 and calretinin are positive in peritoneal type inclusion cysts.
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Reference: Epithelial inclusion cyst
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Reference: Epithelial inclusion cyst
