Placenta
Gestational trophoblastic disease
Exaggerated placental site

Author: Sonali Lanjewar, M.D., MBBS (see Authors page)
Editor: Ravi Gupta, M.D.

Revised: 20 October 2017, last major update July 2017

Copyright: (c) 2002-2017, PathologyOutlines.com, Inc.

PubMed Search: Exaggerated placental site

Cite this page: Lanjewar, S. Exaggerated placental site. PathologyOutlines.com website. http://pathologyoutlines.com/topic/placentaexagg.html. Accessed November 22nd, 2017.
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

Images hosted on PathOut server:

Images contributed by Sonali Lanjewar M.D., MBBS:

Invasion of myometrium by intermediate trophoblasts

Numerous multinucleate intermediate trophoblasts infiltrating the myometrium (left: 10x; right: 20x)

Positive stains
Negative stains
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 question #1
Exaggerated placental site is characterized by:

  1. Absence of villi
  2. Presence of necrosis and mitoses
  3. Proliferation of chorionic type intermediate trophoblasts with invasion of myometrium and blood vessels
  4. Proliferation of implantation type intermediate trophoblasts with invasion of myometrium and blood vessels
Board review answer #1
D. Proliferation of implantation type intermediate trophoblasts with invasion of myometrium and blood vessels