What is the typical placental description in a case of placenta percreta in an adult female with a history of previous uterine surgery or placenta previa?

Placental Description in Placenta Percreta

Placenta percreta is characterized pathologically as PAS Grade 3E, defined by microscopic evidence of extravillous trophoblast (EVT) or chorionic villi invading into extrauterine tissues such as perivesical fat, parametrium, or bladder wall, rather than true villous penetration through the entire uterine wall. 1

Gross Pathologic Features

On macroscopic examination, placenta percreta demonstrates:

• Deep myometrial invasion with <25% preservation of normal uterine wall thickness relative to uninvolved myometrium 1
• Disruption of the uterine serosal surface (Grade 3D) or adherence to extrauterine structures such as bladder or parametrium (Grade 3E) 1
• Irregular placental-myometrial interface without the gradual wedge-shaped transition seen in cesarean scar dehiscence alone 1
• Two distinct invasion patterns: direct infiltrative invasion showing abrupt transition from normal myometrium to placental tissue, or implantation overlying cesarean scar dehiscence with gradual thinning 1

Microscopic Histologic Features

The definitive histologic diagnosis requires:

• Extravillous trophoblast (EVT) extending into perivesical adipose tissue or parametrial fat 1
• Chorionic villi or EVT documented in extrauterine tissues (bladder wall, parametrium, or other pelvic organs) 1
• Absence of decidua basalis at the placental-myometrial interface 1
• Trophoblastic conversion of subserosal blood vessels with EVT infiltration to within microns of the serosal surface 1

Anatomic Location and Extent

Reporting should specify:

• Location of implantation: most commonly anterior lower uterine segment adjacent to bladder in patients with prior cesarean delivery 1, 2
• Estimated percentage of placental bed involved in invasion 1
• Area of serosal disruption measured in cm² if present 1
• Specific extrauterine structures involved (bladder most common, followed by parametrium) 1

Associated Findings

Common concurrent pathologic features include:

• Cesarean scar dehiscence: uterine wall thinned to only a few millimeters, composed entirely of fibrotic scar tissue 1, 3
• Massively dilated vessels at the uteroplacental interface that may simulate vascular continuity on imaging 1
• Blood clot accumulation in areas of scar dehiscence 1
• Distorted, dilated, and tortuous subserosal blood vessels in areas of fibrotic scarring 1

Critical Diagnostic Pitfalls

Avoid these common errors:

• Do not diagnose percreta based solely on surgeon's intraoperative impression without microscopic confirmation of EVT in extrauterine fat 1
• Do not diagnose percreta when villi are present at an inked margin without documented invasion into adipose tissue 1
• Do not grade PAS based on cesarean scar dehiscence area alone—sections must include adjacent myometrium showing infiltrative invasion 1
• Distinguish surgical disruption from true invasion: correlation with surgical and radiographic findings is essential when specimen integrity is compromised 1

Modern Classification Context

The 2020 expert panel recommendations emphasize:

• Moving away from the traditional "accreta/increta/percreta" terminology toward descriptive PAS grading (Grades 1-3E) to improve reproducibility 1
• Grade 3E captures all extrauterine invasion regardless of specific organ involved, aligning with FIGO clinical classification 1
• Histologic confirmation requires EVT in extrauterine tissues, not merely villi extending through bladder wall into lumen 1

Recent research challenges the concept that villous tissue truly penetrates the entire uterine wall in percreta, suggesting most cases result from uterine rupture or preexisting uterine pathology rather than abnormally invasive placentation 4. However, the pathologic definition remains based on documented extrauterine trophoblastic tissue 1.