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Placenta

Gestational trophoblastic disease

Epithelioid trophoblastic tumor

Reviewers: Mandolin Ziadie, M.D. (see Reviewers page)
Revised: 7 December 2011, last major update December 2011
Copyright: (c) 2003-2011, PathologyOutlines.com, Inc.

Clinical features
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● Rare (< 50 cases reported) trophoblastic tumor resembling poorly differentiated carcinoma in women of reproductive age
● Attributed to neoplastic transformation of chorionic-type intermediate trophoblast
● Less aggressive than choriocarcioma, but may recur or metastasize; 10% die of disease
● Usually presents with abnormal vaginal bleeding and elevated serum hCG
● May be diagnosed 10 years+ after last known pregnancy; may also follow elective abortion or mole
● May be associated with choriocarcinoma
● Rarely diagnosed initially in lungs

Treatment
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● Hysterectomy, pulmonary resections
● Chemotherapy (partial response)

Gross description
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● 1-4 cm, tan-brown, discrete expansile nodule in endomyometrium of lower uterine segment or uterine cervix with hemorrhage and necrosis

Micro description
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● Atypical mononuclear trophoblastic cells with abundant eosinophilic cytoplasm, large irregular nuclei and nucleoli; arranged in nests and cords and sheets that have an expansile invasion pattern, often with rim of lymphocytes at periphery
● Resembles squamous cell carcinoma
● Cells are surrounded by fibrillar hyaline material that may coalesce and is easily confused with keratin
● Prominent cellular necrosis
● Lumina of blood vessels contain fibrinoid material but NO tumor cells
● May replace or re-epithelialize endocervical or endometrial surface epithelium
● Mean 2 mitotic figures / 10 HPF
● Apoptotic cells common
● Cells resemble those in placental site nodule

Positive stains
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● CK18, HLA-G, inhibin-alpha and Ki-67 (20%)

Negative stains
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● hCG, hPL and Mel-CAM (may be focal+)

Differential diagnosis
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● Placental site trophoblastic tumor: diffuse Mel-CAM+, hPL+
● Placental site nodule: microscopic, no necrosis, hypocellular and high Ki-67
● Keratinizing squamous cell carcinoma of cervix: fewer stratified epithelial layers, even when it replaces surface endocervical cells, cells perpendicular not parallel to basement membrane, CK18- and inhibin-alpha negative

End of Placenta > Gestational trophoblastic disease > Epithelioid trophoblastic tumor

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