Placenta
Gestational trophoblastic disease
Nonneoplastic lesions
Exaggerated placental site
Authors: Sonali Lanjewar, M.B.B.S., Raavi Gupta, M.D.
Topic Completed: 1 July 2017
Minor changes: 1 March 2021
Copyright: 2002-2021, PathologyOutlines.com, Inc.
PubMed Search: Exaggerated placental site
Table of Contents
Definition / general | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Negative stains | Differential diagnosis | Board review style question #1 | Board review style answer #1Cite this page: Lanjewar S, Gupta R. Exaggerated placental site. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/placentaexagg.html. Accessed March 4th, 2021.
Definition / general
- Exuberant infiltration of myometrium by implantation site intermediate trophoblasts
- Seen in 1.6% of first trimester abortions but can also occur after full term pregnancy
- Pleomorphism of intermediate trophoblastic cells, together with their physiological capacity to invade blood vessels and myometrium, can cause them to be confused with neoplastic conditions like placental site trophoblastic tumor
- Rarely, can cause life threatening hemorrhage (Tohoku J Exp Med 2014;234:77)
- Resolves spontaneously after curettage
- No specific treatment or follow up is necessary
Microscopic (histologic) description
- Extensive infiltration of endometrium and myometrium by implantation site intermediate trophoblasts, some multinucleated
- Endometrial glands and spiral arterioles can show engulfment by trophoblasts
- Smooth muscle cells of myometrium are separated by cords, nests and individual trophoblastic cells that diffusely infiltrate the myometrium
- Despite diffuse infiltration, there is no necrosis and no mitoses
- Trophoblastic cells share similar morphological features of normal implantation site intermediate trophoblastic cells; these cells contain abundant eosinophilic cytoplasm with hyperchromatic and irregular nuclei
- Chorionic villi are morphologically unremarkable
Microscopic (histologic) images
Contributed by Sonali Lanjewar, M.D., M.B.B.S.
Invasion of myometrium by intermediate trophoblasts
Numerous multinucleate intermediate trophoblasts infiltrating the myometrium (left: 10x; right: 20x)
Differential diagnosis
- Choriocarcinoma: extensive hemorrhage and necrosis but no chorionic villi
- Epithelioid trophoblastic tumor or placental site nodule
- Proliferation of chorionic type intermediate trophoblastic cells
- Strongly positive for p63, focally positive for hPL and Mel-CAM / CD146, negative for MUC4
- Placental site trophoblastic tumor (PSTT): histologic features that favor the diagnosis of PSTT include
- Confluent sheets of trophoblastic cells
- Increased mitoses (Ki67 → 10% vs. Ki67 - 0 in EPS)
- No chorionic villi
- Exaggerated placental site is microscopic in size, lacks mitotic activity and is admixed with decidua and chorionic villi
Board review style question #1
Exaggerated placental site is characterized by:
- Absence of villi
- Presence of necrosis and mitoses
- Proliferation of chorionic type intermediate trophoblasts with invasion of myometrium and blood vessels
- Proliferation of implantation type intermediate trophoblasts with invasion of myometrium and blood vessels
Board review style answer #1
D. Proliferation of implantation type intermediate trophoblasts with invasion of myometrium and blood vessels
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Reference: Exaggerated placental site
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Reference: Exaggerated placental site
