Endometrioid tumors
Endometrioid carcinoma

Topic Completed: 1 December 2012

Minor changes: 1 December 2020

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PubMed search: Ovarian endometrioid carcinoma

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Cite this page: Ehdaivand S. Endometrioid carcinoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/ovarytumorendometrioidcarcinoma.html. Accessed January 16th, 2021.
Definition / general
  • 10 - 25% of primary ovarian carcinomas
  • 15% coexist with endometriosis; tumors may arise from endometriotic cysts
  • 15 - 30% of patients have synchronous endometrial hyperplasia or carcinoma; these tumors are often well differentiated with squamous metaplasia
  • Associated with keratin granulomas of peritoneum, which are devoid of viable cells; may contain ghosts of squamous cells or keratin debris
  • Search for viable tumor cells; but granulomas alone do not change stage or prognosis (Am J Surg Pathol 1990;14:925)
  • Mean age 51 years, range 26 - 87 years
  • Grading: similar to primary carcinomas in the endometrium
Prognostic factors
  • Better than serous / mucinous tumors because usually stage 1 and well differentiated, but when matched for age, stage and grade, prognosis is similar to serous
  • Cytologic atypia and microinvasion do not appear to affect prognosis (Am J Surg Pathol 2000;24:1465)
  • Prognosis not as good as borderline tumors; may have malignant behavior if limited destructive stromal invasion (Mod Pathol 2005;18:903)
  • Sample thoroughly, as serous or undifferentiated carcinoma component lowers 5 year survival from 63% (pure) to 8% (Am J Surg Pathol 1994;18:687)
  • Tumors with yolk sac component are unusually aggressive (Am J Surg Pathol 1996;20:1056)
Gross description
  • Cystic, solid, hemorrhagic
  • Papillary formations are absent or inconspicuous
  • 5% bilateral
  • Mean 11 cm, range 3 - 22 cm
Gross images

AFIP images

Surface of ovary and opened uterus

Arising in endometriotic cyst

Contributed by Ayse Ayhan, M.D.

Bilateral endometrioid cancer:

Left: 730g, 14.5x12.6cm

Ovarian tumor:

Right: 70g, 7.5x3.5cm

Images hosted on other servers:

Focal necrosis

Microscopic (histologic) description
  • Either non-cystic villoglandular pattern, glandular confluence or stromal disappearance
  • Stromal invasion is defined as confluent glandular growth, stromal disappearance or obvious stromal invasion
  • Resembles endometrioid adenocarcinoma of endometrium, usually well differentiated
  • 50% have squamous metaplasia (morules or keratin pearls, formerly called adenoacanthomas), 40% of well differentiated tumors have adenofibromatous component
  • 10% are associated with luteinized stroma cells
  • May contain luminal but not cytoplasmic mucin, may have clear cells (but lacks the architecture of clear cell carcinoma, Am J Surg Pathol 2007;31:1203)
  • Vascular invasion rare
Microscopic (histologic) images

AFIP images

Endometrioid adenocarcinoma

Balloon type vacuoles

Over half the tumor is solid

Predominantly undifferentiated

Spindle shaped

Pattern of adenoid basal carcinoma

With squamous differentiation

Oxyphilic variant

Ciliated cell variant

Secretory variant

Foreign body giant cell reaction

Lining endometriotic cyst

Positive stains
Molecular / cytogenetics description
  • PTEN mutations in 21%
Electron microscopy description
  • Paranuclear microfilaments, "mesh basket" nucleoli
Differential diagnosis
  • Granulosa cell or Sertoli-Leydig tumors: usually younger patients with endocrine symptoms, no squamous metaplasia, no typical endometrioid features elsewhere, no mucin, no adenofibroma component, keratin negative
  • Metastatic colonic carcinoma: dirty necrosis, garland pattern, CDX2+, CK20+
  • Metastatic endometrial carcinoma: high grade, bilateral, multinodular, surface implants, prominent angiolymphatic invasion within ovarian stroma
  • Mixed endometrioid and mucinous ovarian carcinoma: > 10% mucinous component
  • Yolk sac tumors
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