Peritoneal carcinomatosis
Synonyms and keywords: Peritoneal metastases; Peritoneal seeding

# Overview
Peritoneal carcinomatosis (also known as peritoneal metastases) is defined as a malignant tumor of the peritoneum. Metastases are the most common peritoneal malignancy, commonly metastasize from ovarian cancer, colon cancer, gastric cancer, and pancreatic cancer.  Calcified peritoneal carcinomatosis may occur in serous ovarian adenocarcinoma, colon cancer, and gastric cancer. Peritoneal carcinogenesis arises from the celomic epithelium lining of the abdominal cavity (peritoneum) in response to an oncogenic stimulus. Common causes of peritoneal carcinomatosis, include: peritoneal mesothelioma, colon cancer, gastric cancer, and pancreatic cancer. Early clinical features include abdominal pain, abdominal distension, and nausea. If left untreated, the majority of patients with peritoneal carcinomatosis may progress to develop portal hypertension, pulmonary edema, and death. Common complications of peritoneal carcinomatosis include intestinal obstruction and pulmonary thromboembolism. The diagnosis of peritoneal carcinomatosis, include: Imaging findings compatible with peritoneal carcinomatosis, elevated protein concentration (more than 4.0 g/dL) in ascitic fluid, abnormal serum-ascites albumin gradient (less than 1.1 g/dL) in ascitic fluid, and high cell count (lymphocyte predominance). The mainstay medical therapy for peritoneal carcinomatosis is hyperthermic intraperitoneal chemotherapy (HIPEC), followed by cytoreductive surgery, laparotomy in conjunction with cytology testing is the most common approach for the treatment of peritoneal carcinomatosis. Prognosis is generally poor, and the 5-year survival rate of patients with peritoneal carcinomatosis is approximately 20%.

# Historical Perspective
- Peritoneal carcinomatosis was first described by Swerdlow in 1959.

# Classification
According to the Gilly classification, peritoneal carcinomatosis may be classified according to nodule size and intraperitoneal involvement (localized or diffuse) into 4 categories:
- 0 - No macroscopic disease
- 1 - Malignant granulations less than 5 mm in diameter localized in one part of the abdomen
- 2 - Malignant granulations less than 5 mm in diameter diffuse to the whole abdomen
- 3 - Localized or diffuse malignant granulations 520 mm in diameter
- 4 - Localized or diffuse large malignant masses (more than 2 cm in diameter)

# Pathophysiology
- The pathogenesis of peritoneal carcinomatosis is characterized by the malignant seeding of a tumor in the peritoneal cavity.
- Peritoneal carcinogenesis arises from the celomic epithelium lining of the abdominal cavity (peritoneum) in response to an oncogenic stimulus.
- The mutation on BRCA1/BRCA2  has been associated with the development of peritoneal carcinomatosis.
- On gross pathology, characteristic findings of peritoneal carcinomatosis, include:
Multilocular thin-walled cysts containing serous fluid
Occasionally unilocular
May be up to 15 cm
Adherent to the surface
- Multilocular thin-walled cysts containing serous fluid
- Occasionally unilocular
- May be up to 15 cm
- Adherent to the surface
- On microscopic histopathological analysis, characteristic findings of peritoneal carcinomatosis, include:
Thin-walled, irregular-shaped cysts
Mesothelial lining
Squamous metaplasia
Eosinophilic fluid
- Thin-walled, irregular-shaped cysts
- Mesothelial lining
- Squamous metaplasia
- Eosinophilic fluid

# Causes
Common causes of peritoneal carcinomatosis, include:
- Peritoneal mesothelioma
- Colon cancer
- Gastric cancer
- Pancreatic cancer
Peritoneal carcinomatosis may also be caused by a mutation in the BCRA1 or BCRA2  genes.

# Differentiating Peritoneal Carcinomatosis from Other Diseases
Peritoneal carcinomatosis must be differentiated from other diseases that cause abdominal pain, ascites, and weight loss, such as:
- Peritoneal mesothelioma
- Peritoneal tuberculosis
- Pseudomyxoma peritonei
- Spontaneous bacterial peritonitis (SBP)
- Secondary bacterial peritonitis

# Epidemiology and Demographics
- The prevalence of peritoneal carcinomatosis is approximately 0.03 per 100,000 individuals worldwide.

## Age
- Peritoneal carcinomatosis is more commonly observed among patients aged 50 - 70 years.
- Peritoneal carcinomatosis is more commonly observed among adults.

## Gender
- Females are more commonly affected with peritoneal carcinomatosis than males.

## Race
- There is no racial predilection for peritoneal carcinomatosis.

# Risk Factors
The most important  risk factor in the development of peritoneal carcinomatosis include:
- Ovarian cancer
- Colon cancer
- Gastric cancer
- Pancreatic cancer

# Natural History, Complications and Prognosis
- The majority of patients with peritoneal carcinomatosis may be initially asymptomatic.
- Early clinical features include abdominal pain, abdominal distension, and nausea.
- If left untreated, the majority of patients with peritoneal carcinomatosis may progress to develop portal hypertension, pulmonary edema, and death.
- Common complications of peritoneal carcinomatosis include intestinal obstruction and pulmonary thromboembolism.
- Prognosis is generally poor, and the 5 year survival rate of patients with peritoneal carcinomatosis is approximately 20%.

# Diagnosis

## Diagnostic Criteria
The diagnosis of peritoneal carcinomatosis is made when at least the following diagnostic criteria are met:
- Imaging findings compatible with peritoneal carcinomatosis (see below)
- Elevated protein concentration (more than 4.0 g/dL)
- Abnormal serum-ascites albumin gradient (less than 1.1 g/dL)
- High cell count (lymphocyte predominance)

## Symptoms
- Peritoneal carcinomatosis is usually asymptomatic.
- Symptoms of peritoneal carcinomatosis may include the following:
- Abdominal distension
- Nausea
- Bloating
- Intermittent abdominal pain
- Vomiting
- Alternating diarrhea and constipation

## Physical Examination
- Patients with peritoneal carcinomatosis usually appear pale and lethargic.
- Physical examination may be remarkable for:
Inspection
- Enlarged abdomen
- Abdominal distension
Palpation
- Bulging of the flanks or shifting dullness
- Fluid thrill or fluid wave
- Other physical examination findings may include:
- Leg swelling
- Bruising
- Gynecomastia

## Laboratory Findings
- Laboratory findings consistent with the diagnosis of peritoneal carcinomatosis, include:
- Elevated carcinoembryonic antigen (unspecific)
- Elevated cancer antigen 125 (unspecific)
- Elevated cancer antigen 19-9 (unspecific)

## Imaging Findings
- Enhanced CT scan is the imaging modality of choice for peritoneal carcinomatosis.
- On CT, peritoneal carcinomatosis is characterized by the following findings:
- Smooth or nodular peritoneal thickening and enhancement.
- Implants on the liver and the splenic surfaces are frequently seen and result in scalloping of the surface by the masses.
- Sites of tumor implantation are the intersegmental fissure, superior recess of the lesser sac, subphrenic space, and Morison pouch.
- Usually there is large ascites, which is often loculated.
- The images below demonstrate a case of peritoneal carcinomatosis.

## Other Diagnostic Studies
- Peritoneal carcinomatosis may also be diagnosed using abdominal paracentesis.
- Findings on paracentesis may include:
- Opalescent appearance
- Elevated protein concentration (more than 4.0 g/dL)
- Abnormal serum-ascites albumin gradient ( less than 1.1 g/dL )
- Other diagnostic studies, include: positron emission tomography (PET)/PET-CT, diagnostic laparoscopy, ultrasonography, magnetic resonance imaging (MRI)

# Treatment

## Medical Therapy
- The mainstay medical therapy for peritoneal carcinomatosis is hyperthermic intraperitoneal chemotherapy (HIPEC).
- Common chemotherapy agents, include:
Mitomycin
Cisplatin
Oxaliplatin
Doxorubicin
Mitoxantrone
- Mitomycin
- Cisplatin
- Oxaliplatin
- Doxorubicin
- Mitoxantrone

## Surgery
- Cytoreductive surgery is the mainstay of therapy for peritoneal carcinomatosis.
- Laparotomy in conjunction with cytology testing is the most common approach to the treatment of peritoneal carcinomatosis.
- Cytoreductive surgery is composed of three steps: Exploration of the abdominal cavity, debulking and chemoperfusion.

## Prevention
- There are no primary preventive measures available for peritoneal carcinomatosis.
- Once diagnosed and successfully treated, patients with peritoneal carcinomatosis are followed-up every 1, 3 or 6 months.
- Follow-up testing includes ultrasound, paracentesis, and abdominal examination.