Placenta
Gestational trophoblastic disease
Nonneoplastic lesions
Placental site nodule
Authors: Sonali Lanjewar, M.B.B.S., Raavi Gupta, M.D.
Editorial Board Member: Carlos Parra-Herran, M.D.
Topic Completed: 1 October 2017
Minor changes: 13 August 2020
Copyright: 2002-2021, PathologyOutlines.com, Inc.
PubMed Search: Placental site nodule
Table of Contents
Definition / general | Clinical features | Gross description | 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. Placental site nodule. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/placentaplacentalsitenodule.html. Accessed January 23rd, 2021.
Definition / general
- Placental site nodules (or plaques) are small and well circumscribed nodular aggregates of intermediate trophoblastic cells embedded in a hyalinized stroma
- Represent the benign counterpart of the epithelioid trophoblastic tumor
- Atypical placental site nodule (ASN) is a term assigned to placental site nodules with significant nuclear atypia and/or borderline proliferation index (see below)
Clinical features
- Discovered incidentally in uterine or endocervical curettings, cervical biopsies and rarely in hysterectomy specimens
- Placental site nodules have been detected in fallopian tubes, presumably a consequence of prior tubal pregnancy (Int J Gynecol Pathol 2003;22:362, Int J Gynecol Pathol 1997;16:219)
- Due to small size and circumscription, these lesions are usually completely surgically excised by curettage
- These lesions are not known to recur or progress to persistent gestational trophoblastic disease (Int J Gynecol Pathol 2001;20:31)
- No specific treatment or follow up is necessary for this lesion
- The behavior of atypical placental site nodule has not yet been studied
Gross description
- Placental site nodules are small lesions, from 1 to 14 mm (average 2.1 mm)
- Grossly, these appear as a yellow, white and necrotic appearing nodule in the endometrium or superficial myometrium
Microscopic (histologic) description
- Small nodular or plaque-like lesions with rounded, well circumscribed borders which are surrounded by chronic inflammatory cells and occasionally decidualized stroma
- Nodules typically are composed of haphazardly arranged extravillous trophoblast
- Most trophoblast cells are of "immature (epithelioid) extravillous” type (p63+, CD146-); a minor component of "mature extravillous” type trophoblast (p63-, CD146+) can be seen (Mod Pathol. 2017;30(2s):301A [abstract #1210])
- Trophoblast is usually distributed in the outer portion of nodule around a central hyalinized extracellular matrix
- Mitotic figures are absent or rare
- Cells vary in size and have relatively small uniform nuclei
- Cytoplasm of the larger trophoblastic cells is abundant and eosinophilic; the smaller cells contain glycogen rich clear cytoplasm (Kurman: Blaustein's Pathology of the Female Genital Tract, 6th Edition, 2011)
- Ki67 proliferation index is low (< 8%)
- Atypical placental site nodules: placental site nodule with moderate to severe atypia and Ki67 proliferation index 8 - 10% (Kurman: WHO Classification of Tumours of the Female Reproductive Organs, 4th Edition, 2014)
- These lesions may represent a transition from benign placental site nodule to epithelioid trophoblastic tumor (Int J Gynecol Pathol 2015;34:152)
Microscopic (histologic) images
Contributed by Sonali Lanjewar, M.D., M.B.B.S.
Well circumscribed
nodules with
central
hyalinized matrix
Haphazardly arranged intermediate trophoblasts
Hyalinized matrix and intermediate trophoblasts
Chorionic type intermediate trophoblasts
Weak hPL staining
Positive stains
Differential diagnosis
- Epithelioid trophoblastic tumor (ETT)
- These are larger lesions, more cellular, have extensive necrosis and evident mitoses
- Calcifications are typically present in ETTs and when present, lesion is more likely to be an ETT than placental site nodule
- Cyclin E is expressed in ETT and absent in placental site nodule
- Ki67 index is high (> 10%)
- Squamous cell carcinoma of the cervix
- Circumscription, abundant eosinophilic extracellular deposit and lack of mitotic activity favor a placental site nodule
- Placental site nodules are typically negative for p16
Board review style question #1
The typical immunophenotypic profile of placental site nodule is:
- p63-, hPL-, cyclin E+
- p63-, hPL+, cyclin E-
- p63-, hPL+, cyclin E+
- p63+, hPL+, cyclin E-
Board review style answer #1
