Case 70

A 26 year old woman with full term pregnancy, delivered a dead fetus with a clinical diagnosis of partial hydatidiform mole.

1. What's your diagnosis?

   A: Partial mole

   B: Complete mole

   C: Hydropic changes

   D: Mesenchymal dysplasia

Answer

The correct answer is D. It's a case of placental mesenchymal dysplasia.

Histologic Findings:

• Mature chorionic villi alongside large, variably sized villi with central edema and myxoid areas.

• Large blood vessels with thick muscular walls and fibroblastic proliferation in some villi.

• Markedly increased vascularity, resembling chorangiomatosis, with hemorrhage.

• No trophoblastic proliferation, trophoblastic inclusions, or polar trophoblast, ruling out partial hydatidiform mole.

• Normal umbilical cord and membranes.

  Discussion:

  • Rare condition often mistaken for partial hydatidiform mole on clinical and ultrasound findings.

  • First described in 1991 by Mascosa et al.

  • Associated with increased risk of intrauterine death, fetal growth restriction, and Beckwith-Wiedemann syndrome (macrostomia, visceromegaly, macroglossia, adrenal cysts).

  • Unlike molar pregnancy, PMD can progress into the third trimester, though live births are rare.

  • Etiology uncertain, with proposed theories including congenital mesodermal malformation, hypoperfusion, and androgenetic mosaicism.

  • Chromosomal abnormalities associated with PMD include trisomy 13, Klinefelter syndrome, and triploidy.

References: https://www.pathologyoutlines.com/topic/placentapmd.html

Case credit: https://qp.91360.com/43.html?lang=en

Author: Wangpan Jackson Shi, MD