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Gestational trophoblastic disease

Exaggerated placental site

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


● Benign, non-neoplastic and noninflammatory lesion caused by hyperplasia and endometrial infiltration of intermediate trophoblasts and syncytiotrophoblasts at the site of implantation
● Identified in 2% of normal pregnancies or abortions in first trimester
● Treatment is unnecessary
● Patients are followed with serum hCG if a placental site trophoblastic tumor cannot be excluded

Micro description

● Excess mononuclear intermediate trophoblasts and multinucleated syncytiotrophoblasts that infiltrate the endomyometrium as single cells and cords of cells
● May have necrotic decidua, but no necrosis, no destruction of endometrial glands

Positive stains

● CK18, HLA-G (Am J Surg Pathol 2002;26:914), hPL
● Mel-CAM, inhibin (weak)

Negative stains

● hCG, Ki-67 (close to 0, Hum Pathol 1998;29:27), PLAP

Differential diagnosis

● Placental site nodule: well-circumscribed, extensive hyalinization
● Placental site trophoblastic tumor: macroscopic tumor that invades the myometrium, mean Ki-67 is 14% of cells vs. 0%, no associated decidua or villi, confluent masses of implantation-site intermediate trophoblastic cells and often no multinucleated trophoblastic cells
● Choriocarcinoma or epithelioid trophoblastic tumor: marked atypia, necrosis and vascular invasion

End of Placenta > Gestational trophoblastic disease > Exaggerated placental site

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