| Partial mole | Complete mole |
Fetus | - Present*
- Syndactyly involving digits 3 and 4, especially of the hand*
| |
Cytotrophoblasts | - Mild atypia and proliferation*
| - Often atypical, significant and focally extreme proliferation*
|
Syncytiotrophoblasts | - Mild atypia and proliferation*
|
Implantation site extravillous (intermediate) trophoblasts | |
Chorionic membranous extravillous (intermediate) trophoblasts | - Chorion and amnion usually present*
| |
Chorionic villi | - Biphasic – having normal and enlarged, irregularly shaped populations with scattered cavitated villi*
| - "Classic" lesions have diffusely enlarged and frequent villous cavitation*
- Early lesions have myxoid basophilic (blue) stroma and deep, narrow inclusion of surface trophoblast layer*
|
Biological potential | - Mostly benign, even when hCG persists
- Rarely associated with choriocarcinoma, PSTT, or ETT
| - Invasive or metastatic in approximately 20% of cases
|
Differential diagnosis | - Aneuploid gestation (eg, trisomy 11, 13, 18, or 21)
- Complete hydatidiform mole plus normal co-twin
- Mesenchymal dysplasia and Beckwith-Wiedemann syndrome (p57 abnormalities cause by different mechanism)
| - Hydropic (degenerating) abortus
- Partial hydatidiform mole
- Unusual complete hydatidiform mole-like chimeric/mosaic gestations
|
Typical genetics | - Diandric triploid gestations (69,XXX, 69,XXY, rarely 69,XYY) with 2 sets of paternal chromosomes
| - 46,XX karyotype, with all chromosomes of paternal origin
- Rarely, familial and biparental inheritance can occur due to germline mutations of NRLP7, KHDC3L, or PADI6
|
Key marker status | - p57 immunostaining retained
| - p57 immunostaining is absent in villous cytotrophoblasts and stromal cells
|