Placental site nodule

Placental site nodule, abbreviated PSN, is a benign remnant of a placenta. It is seen on endometrial biopsies and hysterectomy specimens.

Placental site nodule
Diagnosis in short
LM	paucicellular hyaline material scattered cells (variable cell population: small to large cells with clear to eosinophilic cytoplasm), +/-multinucleation, no mitotic activity
Site	endometrium
Clinical history	previously pregnant
Symptoms	none
Prevalence	common
Prognosis	benign
Treatment	none

Implantation site redirects here.

General

• Benign.
• Intermediate trophoblast remnants from a previous gestation.
• Usually an incidental finding.

Clinical:

• Usually asymptomatic.
• Vaginal bleeding. (?)
• Infertility. (?)

Microscopic

Features:

• Paucicellular with hyaline material scattered cells.
• Variable cell population:
  • Small-large cells.
  • Clear to eosinophilic cytoplasm.
  • +/-Multinucleation.

Notes:

• No mitotic activity.

DDx:

• Invasive (cervical) squamous cell carcinoma.
  • Can be sorted-out with IHC (SCC will typically be: p16 +ve, MIB1 +ve).
• Exaggerated placental site.
  • Different histomorphology than PSN; EPS: syncytiotrophoblastic tissue, in cords/nests, no hyaline nodules.
• Fibrin +/-inflammatory cells.

Images

• 

  PSN - intermed. mag. (WC)

• 

  PSN - high mag. (WC)

www

• PSN (ijpmonline.org).
• PSN (gfmer.ch) - includes images from Jacob and Mohapatra.

IHC

Features:

• Inhibin alpha +ve.
• CK18 +ve.
• MIB1 low.

Other:

• p16 -ve.

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- CONSISTENT WITH MENSTRUAL ENDOMETRIUM (FRAGMENTED ENDOMETRIUM WITH SIMPLE
  GLANDS WITH APOPTOTIC CELLS, ABUNDANT NEUTROPHILS, CONDENSED ENDOMETRIAL STROMA
  (FOCAL) AND BLOOD).
- PLACENTAL SITE NODULE AND DECIDUA.
- NEGATIVE FOR HYPERPLASIA AND NEGATIVE FOR MALIGNANCY.

ENDOMETRIUM, BIOPSY:
- PROLIFERATIVE PHASE ENDOMETRIUM.
- BENIGN PLACENTAL SITE NODULE, SMALL.
- NEGATIVE FOR HYPERPLASIA.

See also

• Gestational trophoblastic disease.
• Endometrium.