Placenta - Placental site nodule

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Placenta

Gestational trophoblastic disease

Placental site nodule

Reviewers: Mandolin Ziadie, M.D. (see Reviewers page)
Revised: 16 November 2011, last major update October 2011
Copyright: (c) 2003-2011, PathologyOutlines.com, Inc.

Definition
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● Nodule composed of benign cells similar to those in the chorion lavae; often an incidental finding on endometrial biopsies / endocervical curettage
● Remnant of implantation site that failed to involute; may be identified many years after pregnancy
● Women may complain of abnormal bleeding
● No treatment required

Gross description
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● Yellow-tan nodular or plaquelike lesion(s) at placental site, up to 1 cm, often in endometrial curettings

Micro description
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● Well-circumscribed, extensively hyalinized and paucicellular, oval or plaquelike nodule(s)
● Cells are chorionic-type intermediate trophoblast cells with abundant eosinophilic, amphophilic or clear (glycogen-rich) cytoplasm, irregular / degenerative appearing nuclei
● No/rare mitotic figures (Am J Surg Pathol 1990;14:1001)
● May contain mallory bodies (Arch Pathol Lab Med 1993;117:547)

Positive stains
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● CK18, EMA, HLA-G (Am J Surg Pathol 2002;26:914), inhibin-alpha (strong), Ki-67 (3-10%) and PLAP

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

Differential diagnosis
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● Placental site trophoblastic tumor: larger, not well circumscribed, no extensive hyalinization, mitotically active, strong staining for hPL and PLAP and weak staining for PLAP
● Squamous cell carcinoma of cervix: necrosis, mitotically active, CK18 and inhibin-alpha negative (Hum Pathol 1999;30:687)
● Epithelioid trophoblastic tumor

End of Placenta > Gestational trophoblastic disease > Placental site nodule

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