Peritoneal Lesions & Staging

Endometriosis can leave spots on the peritoneum — the thin lining of the abdomen — that look like tumor implants, and in ovarian cancer that distinction can change the stage. (pathologyoutlines.com) (pmc.ncbi.nlm.nih.gov) Pathologists define endometriosis as endometrial-type glands and stroma, or chronic bleeding, found outside the uterus. The peritoneum is one of the recognized sites, so tiny pelvic or abdominal lesions can be benign endometriosis rather than spread from a cancer. (pathologyoutlines.com) That matters because the International Federation of Gynecology and Obstetrics groups ovarian, fallopian tube, and primary peritoneal cancers in one staging system. In that system, stage IIIA2 means microscopic peritoneal involvement beyond the pelvis, while stage IIIB and IIIC cover visible peritoneal metastases outside the pelvis by size. (pmc.ncbi.nlm.nih.gov) Surgical staging is built around those findings. European Society of Gynaecological Oncology guidance for apparent early-stage disease recommends peritoneal washings before tumor manipulation, visual inspection of the whole peritoneal cavity, blind peritoneal biopsies from the pelvis, paracolic spaces, and both diaphragms, and at least an infracolic omentectomy. (esgo.org) Patient-facing National Comprehensive Cancer Network guidance says the information gathered during surgery determines the pathologic stage, which is the most accurate measure of spread. The same guideline set treats ovarian, fallopian tube, and primary peritoneal cancers together because management depends on where disease is found at operation and on pathology review. (nccn.org) (jnccn.org) The practical problem is that not every peritoneal gland is cancer. Endosalpingiosis, another benign Müllerian lesion, is usually an incidental microscopic finding on pelvic or abdominal peritoneum and can also enter the differential diagnosis when surgeons or pathologists evaluate implants. (pathologyoutlines.com) For surgeons, that means suspicious peritoneal lesions often trigger more sampling rather than assumptions. British Columbia Cancer’s ovarian cancer surgery guidance says peritoneal washings, peritoneal biopsies, node assessment, and omentectomy are important for detecting subclinical extra-ovarian spread, and advanced-stage planning may include deciding between primary debulking surgery and preoperative chemotherapy. (bccancer.bc.ca) For pathologists, the call can redirect the whole case: benign endometriosis on the peritoneum does not equal metastatic carcinoma, but confirmed extrapelvic peritoneal metastasis can move a patient into stage III disease. In ovarian cancer, a few millimeters on the peritoneal lining can be the difference between a staging pitfall and a treatment decision. (pmc.ncbi.nlm.nih.gov) (pathologyoutlines.com)