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Non tumor


Reviewer: Nat Pernick, M.D. (see Reviewers page)
Revised: 13 November 2011, last major update November 2011
Copyright: (c) 2002-2011, PathologyOutlines.com, Inc.


● Endometrial tissue outside the uterus; closely related to adenomyosis
● Women 20-30 years old, up to 10% of all women affected
● Consists of functional layers of endometrium that go through menstrual changes, although is more proliferative than normal endometrium
● Causes pain, infertility (1/3 of women are infertile)
Causes: regurgitation (retrograde menstruation), metaplasia and angiolymphatic dissemination (to lungs, nodes); metaplastic change of secondary mullerian system represented by pelvic mesothelium
Sites: ovaries > uterine ligaments > rectovaginal septum > pelvic peritoneum > scar
● Rarely in lymph nodes, usually with cuboidal epithelium, no stroma, limited to capsule and resembles tubal epithelium; call endosalpingiosis
● Rarely has extensive intestinal tract involvement, resembling other intestinal diseases (Am J Surg Pathol 2001;25:445)
● May undergo malignant transformation (Hum Pathol 2000;31:456)
● Malignant tumors: endometrioid > clear cell, endometrial stromal sarcoma and MMMT
● Organizing hemorrhage may cause adhesions, ovarian chocolate cysts


Chocolate cyst


● Hormones, surgery (including robotic assisted laparascopy, JSLS 2011;15:387)

Gross description

● Blue cystic nodules surrounded by fibrosis
● Rarely, polypoid masses simulating a neoplasm (Am J Surg Pathol 2004;28:285)

Gross images

Small foci resembling "powder burns"

"Chocolate" cyst

Micro description

● Contains at least two of three features - endometrial glands, endometrial stroma and hemorrhage
● May be a dense fibrous mass
● May undergo mucinous metaplasia (also called endocervicosis or myxoid change)
● Associated with perineurial invasion
● May be associated with skeletal muscle regeneration (Am J Surg Pathol 2010;34:10)

Micro images

Focus of endometriosis

Endometrial glands and stroma in wall of GI tract

Multifocal polypoid endometriosis presenting as huge pelvic masses

p63 expression

Cytology images

Contributed by Dr. Carmen Luz:

Sheet of endometrial epithelium in FNA from abdominal wall

Sheet of endometrial epithelium adjacent to a group of endocervical epithelium and endometrial stroma from an endometrial direct cytology

Round endometrial epithelial group with slight atypia

Positive stains

● CD10 (endometrial stromal cells, Arch Pathol Lab Med 2003;127:1003), p63 (nuclear staining in glandular component, Arch Pathol Lab Med 2007;131:1099)
● Also CK7, ER, PR, usually CA125 (Hum Pathol 2008;39:954)

Differential diagnosis

● Well differentiated adenocarcinoma if endocervicosis present
● Pseudomyxoma peritonei if myxoid change (may also be caused by endometriosis, Am J Clin Pathol 2000;113:860)

Additional references

Wikipedia, eMedicine

End of Uterus > Non tumor > Endometriosis

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