It is significant only because it can be misdiagnosed as a cancer. It may be seen in a completely normal pregnancy.
Diagnosis
It is characterized by nuclear enlargement and may also have any of the following: an irregular nuclear membrane, granular chromatin, centronuclear vacuolization, and pseudonuclear inclusions.[1]
^Arias-Stella, J. (Aug 1954). "Atypical endometrial changes associated with the presence of chorionic tissue". Arch Pathol. 58 (2): 112–28. PMID13170908.
Bibliography
Textbook of Obstetrics by D.C. Dutta Page no. 180. ISBN81-7381-142-3