Ovary-nontumor
Non-neoplastic cysts / other
Differential Diagnosis of small, cystic follicles

Author: Aurelia Busca, M.D. (see Authors page)
Editorial Board review: by Carlos Parra-Herran, M.D.

Revised: 27 June 2016, last major update June 2016

Copyright: (c) 2002-2016, PathologyOutlines.com, Inc.

PubMed search: ovarian cystic follicles
Definition / General
  • Cystic follicle: cyst < 3 cm lined by an inner layer of granulosa cells and an outer layer of theca cells; if 3 cm or larger - follicular cyst
  • Cystic corpus luteum: < 3 cm lined by granulosa and theca cells with extensive luteinization; if 3 cm or larger - corpus luteum cyst
  • Epithelial inclusion cyst: lined by either ciliated (tubal type) or flat (ovarian surface / peritoneal type) epithelium
    • Tubal type inclusion cysts are arbitrarily defined as < 1 cm; if 1 cm or larger – serous cystadenoma
  • Endometriotic cyst: presence of endometrial glands and stroma in the cyst wall, hemosiderin-laden macrophages
  • Polycystic ovarian disease: multiple cortical cystic follicles with hypocellular and fibrotic cortex
  • Other differential diagnoses: cystic granulosa cell tumor and rete ovarii cyst
Essential Features
  • Epithelial inclusion cysts: single layer of tubal ciliated epithelium (PAX8+) or peritoneal flattened cuboidal epithelium (calretinin+) (Int J Gynecol Pathol 2015;34:3)
  • Cystic follicle / follicular cyst: lined by one to several layers of granulosa cells, surrounded by luteinized theca cells
  • Cystic corpus luteum / corpus luteum cyst: lining is convoluted, composed of luteinized granulosa cells and outer theca cells; often with a prominent inner layer of fibrous tissue
  • Cystic granulosa cell tumor: either unilocular or multilocular, with thin walled cysts and monotonous population of round to oval cells with nuclear grooves, Call-Exner bodies and low mitotic activity
  • Endometriosis / endometriotic cysts: lining is composed of columnar cells with elongated, cigar shaped nuclei
    • Tubal differentiation is common (mimicking epithelial inclusion cysts)
    • Cyst is surrounded by dense, endometrial type stroma and is associated with hemosiderin-laden macrophages
Terminology
  • Cystic follicle if < 3 cm; follicular cyst if> 3 cm
  • Cystic corpus luteum if <3 cm; corpus luteum cyst if > 3cm
  • Epithelial inclusion cyst (tubal type) is <1 cm, serous cystadenoma if >1 cm
Epidemiology
  • Epithelial inclusion cysts: any age, but typically postmenopausal
  • Cystic follicle / follicular cyst: most common in non-pregnant women of reproductive age, around menarche and menopause
  • Cystic corpus luteum / corpus luteum cyst: reproductive age, including pregnancy
Pathophysiology
  • Recent evidence suggests that inclusion cysts can be divided in two types according to the cell of origin (Int J Gynecol Pathol 2015;34:3)
    • Peritoneal type inclusion cysts result from invaginations of ovarian surface epithelium
    • Thus, their lining has a peritoneal phenotype (flat to low cuboidal epithelium, positive for calretinin and WT1, negative for PAX8)
    • Tubal type inclusion cysts derive from implantation of tubal epithelium when the ovarian surface is disrupted at the time of ovulation, which technically is a form of endosalpingiosis
    • Their lining has a Mullerian tubal phenotype (columnar ciliated epithelium that is PAX8 and WT1 positive, calretinin negative)
  • Cystic follicle/follicular cyst: follicle fails to rupture and release its ovum
  • Cystic corpus luteum/Corpus luteum cyst: corpus luteum fails to regress following the release of an ovum
Clinical Features
  • Epithelial inclusion cysts: often incidental findings on gross / microscopic examination, asymptomatic
  • Follicular cyst and corpus luteum cyst: can present with menstrual irregularities, may rupture and result in intra-abdominal hemorrhage
Case Reports
Gross Description
  • Cystic follicle / follicular cyst: smooth surface, thin walls, containing watery fluid or blood
  • Cystic corpus luteum / corpus luteum cyst: cyst wall is yellow in color, the cyst filled with blood
Gross Images

Images hosted on other servers:

Corpus luteum cyst

Endometriotic cyst

Follicular cyst

Serous cystadenoma

Micro Images

Images hosted on other servers:

Corpus luteum cyst (fig 4)

Endometriotic cyst