What Is Primary Peritoneal Cancer?

Primary peritoneal carcinoma (PPC) refers to a malignant tumor that originates in the peritoneal mesothelium and grows multifocally and is rarely seen clinically. The histological characteristics are consistent with those of the same type of tumors with the same degree of differentiation in the ovaries, with the ovaries normal or only superficially involved. The disease was first reported by Swerdlow in 1959 as "pelvic peritoneal mesothelioma resembles ovarian papillary cystadenocarcinoma", but it did not attract much attention. In 1977 Kannerstein reported 15 cases, first named "primary peritoneal papillary serous carcinoma", which clearly distinguished this disease from peritoneal malignant mesothelioma. ^[1]

Primary peritoneal cancer

Basic overview of primary peritoneal cancer

Primary peritoneal carcinoma (PPC) refers to a malignant tumor that originates in the peritoneal mesothelium and grows multifocally and is rarely seen clinically. The histological characteristics are consistent with those of the same type of tumors with the same degree of differentiation in the ovaries, with the ovaries normal or only superficially involved. The disease was first reported by Swerdlow in 1959 as "pelvic peritoneal mesothelioma resembles ovarian papillary cystadenocarcinoma", but it did not attract much attention. In 1977 Kannerstein reported 15 cases, first named "primary peritoneal papillary serous carcinoma", which clearly distinguished this disease from peritoneal malignant mesothelioma. ^[1]

Causes of primary peritoneal cancer

The cause is unknown and the source of the tissue is still controversial. There are two main theories: derived from malignant transformation of ovarian tissue on the embryonic migration path; peritoneal epithelium and ovarian epithelium originate from the same mesoderm, both from Embryonal Coelomic Epithelium, and have the potential for Müllerian differentiation , Called the Second Müllerian system, will become cancerous in the future by some carcinogenic stimulus. ^[2]

Examination of primary peritoneal cancer disease

cytology

Laparoscopy or vaginal posterior fornix puncture is used to extract ascites for cytological examination. Malignant tumors are often positive.

peritoneal biopsy

Peritoneal biopsy is of great value in the diagnosis of peritoneal tumors. Laparoscopic biopsy can be used directly, or peritoneal biopsy can be performed by laparotomy.

Immunohistochemistry

The immunohistochemical characteristics are similar to those of serous ovarian cancer. Mucin measurement and Schiff periodate staining were positive, and no hyaluronic acid was produced. Wick et al. Measured the immunohistochemical indicators of peritoneal serous carcinoma, monoclonal antibody keratin, epithelial membrane antigen, CA125 antigen, LeuM1, B72.3 antigen, carcinoembryonic antigen, amylase, LN1, LN2, MB2, S-100 protein and placenta Phosphatase assays were all positive. Zhou et al reported that all cases were positive for EMA and S-100 protein, 75% of cases were positive for CAl25, 88% were positive for CD15, and 38% were positive for placental alkaline phosphatase. ^[3]

Clinical diagnosis of primary peritoneal cancer

Onset is slow and insidious, and there are usually no conscious symptoms in the early stage. When the tumor grows to a certain size or involves other organs, clinical symptoms appear. Abdominal pain, bloating, and increased abdominal circumference are the three most common symptoms. Abdominal pain is not severe, and only abdominal bloating or discomfort is felt. The main signs are abdominal mass and ascites. The abdominal mass is often large and the border is unclear. Ascites increases rapidly and is mostly bloody.

Because there is no specific diagnostic method, the preoperative misdiagnosis rate is high until extensive peritoneal nodules are seen during the operation, and the ovaries are normal or superficially invaded. The diagnosis mainly depends on B-ultrasound, CT, and ascites cytology, and the diagnosis must be performed by peritoneal biopsy. ^[4]

Primary peritoneal cancer is confusing

Celiac tuberculosis

Serum CA125 is a common antigen of various tissues derived from body cavity epithelium. Preoperative examination of serum CAl25 is helpful to identify celiac tuberculosis.

Peritoneal metastasis from ovarian cancer

The main difference between the two is that there is no tumor infiltration in the bilateral ovarian parenchyma of PPC, and immunohistochemistry does not help distinguish it from epithelial ovarian cancer.

Diffuse peritoneal malignant mesothelioma

Symptoms, signs, and degree of disease are similar. They occur in men and have a history of asbestos exposure. Mesothelioma cells have an active function of producing hyaluronic acid. Measuring the level of hyaluronic acid in a patient's serum or ascites is helpful for differential diagnosis. CA125 levels generally do not increase. Under light microscopy, the tumor cells were polygonal or cubic, and the cytoplasm was eosinophilic, without grit. No neutral mucus, negative for D-pas, positive for ausin blue staining, negative for hyaluronidase digestion. Carcinoembryonic antigen is mostly negative. S-100, placental alkaline phosphatase, CA125, and CD15 are also helpful for identification, such as S-100 protein or both alkaline phosphatase or B72.3 positive can exclude peritoneal malignant mesothelioma. Electron microscopy showed slender, hair-like microvilli. ^[4]

Primary peritoneal cancer treatment

surgical resection

Primary peritoneal cancer should strive to completely remove the tumor. Those who cannot completely remove the tumor should perform Debulking Surgery. The residual tumor should be less than 2 cm. It is necessary to emphasize the simultaneous removal of bilateral ovaries to observe the ovarian lesions.

chemotherapy

Chemotherapy drugs are not standardized, and ovarian cancer schemes are still better, that is, DDP-based schemes, such as PAC or CP schemes. ^[5]