Page 522 - Concise Pathology for Exam Preparation ( PDFDrive )

18 Female Genital System 507

Sites Involved (in Decreasing Order of Frequency)

• Ovaries
• Uterine ligaments
• Recto vaginal septum
• Pelvic peritoneum
• Laparotomy scar
• Rarely, in umbilicus, vagina, vulva, appendix

Pathogenesis
Several theories have been proposed to explain endometriosis:
• Regurgitation/transplantation theory: According to this theory, endometriosis occurs
due to regurgitation of menstrual blood through fallopian tubes which transports
endometrial tissue from uterus to peritoneal cavities and other locations. This is the
most widely accepted theory as it explains the genesis of most cases of endometriosis.
• Metaplastic theory: As per this theory, coelomic epithelium gives rise to endometrial
tissue by metaplasia.
• Benign metastasis (vascular or lymphatic dissemination) theory: It explains the
presence of endometrial tissue at extra pelvic sites like lung or lymph nodes.
• The extrauterine stem or progenitor theory: This relatively new theory proposes that
the extrauterine endometrial tissue arises from stem cells derived from bone marrow.
Molecular analysis has shown that endometriotic implants release proinflammatory
factors (IL1b, TNFa, IL6, IL8, PGE2, NGF, VEGF, MCP1, MMPs and TIMPs), which
increase oestrogen levels (PGE2 stimulates local synthesis of oestrogen), promote invasion
and increase survival of extrauterine endometriotic tissue by reducing its immune
clearance. Also, high levels of an enzyme ‘aromatase’ have been demonstrated in these
implants which also contribute to increase oestrogen production.

Clinical Features
• Dysmenorrhoea
• Dyspareunia
• Infertility
• Pelvic pain due to intrapelvic bleeding and periuterine adhesions
• Pain on defecation or urination (due to involvement of bowel or bladder)

Gross Morphology

• Red-yellow-brown, often bilateral, nodules present on or just beneath the serosal surface
of the sites involved.
• Extensive haemorrhage may cause fibrotic adhesions of different layers.
• Large cystic space filled with brown bloody debris, may distort ovaries (chocolate cysts).

Prerequisites for a Histological Diagnosis of Endometriosis
Two of the three following features must be present for a diagnosis of endometriosis:
• Endometrial glands
• Endometrial stroma
• Haemosiderin-laden macrophages

Atypical Endometriosis
Endometriosis is said to be atypical if the epithelium lining the endometriotic cyst shows
atypia without architectural distortion or if there is architectural distortion (glandular
crowding) with atypia.
Atypical endometriosis and endometrioid and clear cell types of endometrial carcinoma
share PTEN and AT-rich interactive domain-containing protein (ARIDA1) mutations sug-
gesting that endometriosis may be a precursor to carcinoma.

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