Primary Peritoneal Cancer: Symptoms, Types, Causes and Treatment

Primary peritoneal cancer (PPC) is a rare but significant malignancy that arises from the lining of the abdominal cavity. Although it shares many similarities with ovarian cancer, it is distinct in its origin and clinical course. Understanding the symptoms, types, causes, and treatment options is crucial for early detection and effective management. This guide brings together the latest evidence to provide a comprehensive overview tailored for patients, caregivers, and healthcare professionals.

Symptoms of Primary Peritoneal Cancer

Primary peritoneal cancer often presents subtly, making early diagnosis a challenge. Because the peritoneum covers the abdominal organs, symptoms can be vague and easily attributed to other conditions. Recognizing the symptom pattern is vital for timely intervention and improved outcomes.

Symptom	Description	Frequency/Context	Source(s)
Abdominal pain	Persistent or progressive discomfort	Common initial complaint	1, 6
Abdominal distension	Swelling or bloating	Frequently observed	1, 6
Bowel changes	Constipation, altered bowel habits	Variable	1
Ascites	Fluid buildup in the abdomen	Often present at diagnosis	1, 5
Early satiety	Feeling full quickly	As disease progresses	1
Weight loss	Unintentional loss	Advanced disease	1

Table 1: Key Symptoms

Understanding the Symptom Spectrum

Primary peritoneal cancer symptoms largely stem from the tumor’s impact on the abdominal cavity and organs.

Abdominal Pain and Distension

• Abdominal pain is often mild at first and may be mistaken for indigestion or gastrointestinal upset. As the tumor grows or spreads, pain can become more severe and persistent 1, 6.
• Distension or bloating results from fluid accumulation (ascites) or tumor masses. Patients may notice their abdomen appears swollen or clothes become tighter 1, 6.

Gastrointestinal and Systemic Manifestations

• Bowel changes like constipation or altered patterns can occur when tumor growth or fluid presses on the intestines 1.
• Ascites is a hallmark of advanced disease. This buildup of fluid can cause discomfort, shortness of breath, and further distension 1, 5.

Non-Specific and Advanced Symptoms

• Early satiety and weight loss are signs that the disease is impacting digestion or has progressed significantly 1.
• Some patients may also experience mild, nonspecific symptoms such as fatigue or loss of appetite, which can delay diagnosis.

Clinical Challenges

• Because these symptoms are common to many benign conditions, PPC is often diagnosed at an advanced stage 1.
• Imaging and diagnostic procedures are essential to differentiate PPC from other abdominal diseases.

Types of Primary Peritoneal Cancer

Primary peritoneal cancer is not a single entity but encompasses several distinct tumor types, each with unique features, behaviors, and outcomes. Understanding these types helps guide diagnosis and treatment decisions.

Type	Key Features	Demographics/Behavior	Source(s)
Serous carcinoma	Resembles ovarian cancer histologically	Women, aggressive, most common	2, 4
Malignant mesothelioma	Linked to asbestos exposure	Older men, aggressive	2, 3
Clear cell carcinoma	Extremely rare, cystic lesions	Women, very few cases reported	6
Multicystic mesothelioma	Benign or indolent, multilocular cysts	Women, pelvic location	2
Leiomyomatosis peritonealis disseminata	Benign, smooth muscle nodules	Women, rare	2
Desmoplastic small round cell tumor	Highly aggressive, unknown origin	Young men, peritoneal cavity	2

Table 2: Main Types of Primary Peritoneal Cancer

The Main Types Explained

Primary Peritoneal Serous Carcinoma

• The most common type, serous carcinoma, is almost indistinguishable from advanced ovarian cancer under the microscope and in clinical presentation 2, 4.
• Predominantly affects women, especially post-menopausal, and is aggressive in nature 2, 4.
• Survival and treatment are similar to high-grade ovarian cancer 4.

Primary Malignant Mesothelioma

• A rare and aggressive tumor, often linked with asbestos exposure 2, 3.
• More common in older men, presenting with diffuse peritoneal thickening or nodular masses 2.
• Outcomes are generally poor due to late diagnosis and rapid progression 2, 3.

Rare Subtypes

• Clear cell carcinoma: Only a handful of cases reported. Presents as a large cystic mass and poses significant diagnostic challenges due to its rarity and similarity to ovarian tumors 6.
• Multicystic mesothelioma: Typically benign, arises from pelvic peritoneal surfaces, more common in women 2.
• Leiomyomatosis peritonealis disseminata: Characterized by multiple smooth muscle nodules, exclusively in women; usually benign 2.
• Desmoplastic small round cell tumor: Highly aggressive and occurs mainly in young men; features small round blue cells within a desmoplastic stroma 2.

Diagnostic Considerations

• Distinguishing PPC from metastatic ovarian or gastrointestinal cancers is difficult and often requires a combination of imaging, histopathology, and sometimes molecular profiling 2, 5, 6.
• Multidisciplinary teams are essential for accurate diagnosis and management 5.

Causes of Primary Peritoneal Cancer

The exact causes of primary peritoneal cancer remain elusive, but several risk factors and mechanisms have been identified. Understanding these can help inform both prevention and surveillance strategies.

Cause/Risk Factor	Description	Evidence/Notes	Source(s)
Mesothelial transformation	Cells lining the peritoneum become malignant	Main mechanism proposed	3, 2
Asbestos exposure	Inhaled fibers reach peritoneal surface	Especially for mesothelioma	2, 3
Genetic predisposition	BRCA1/2 mutations, family history	Shared with ovarian cancer	4
Age and gender	Older age, female sex (serous type)	Epidemiological trends	4, 2
Unknown/idiopathic	Many cases have no clear cause	Ongoing research	3

Table 3: Major Causes and Risk Factors

Understanding the Underlying Mechanisms

Malignant Transformation of Mesothelial Cells

• The peritoneum is lined by mesothelial cells, which can undergo malignant transformation due to chronic irritation, inflammation, or genetic changes 2, 3.
• This process is the primary mechanism for both serous carcinoma and mesothelioma 2, 3.

Environmental and Occupational Exposures

• Asbestos: Strongly linked to peritoneal mesothelioma. Asbestos fibers can be ingested or inhaled, eventually reaching the peritoneum 2, 3.
• Other environmental exposures are less well-documented.

Genetic and Demographic Factors

• BRCA1/2 mutations: Women with these mutations are at higher risk for both ovarian and peritoneal serous carcinomas 4.
• Age and gender: Most cases of serous PPC occur in older women; mesothelioma more often affects older men 2, 4.

Idiopathic and Unexplained Cases

• Many cases arise without any identifiable risk factor, highlighting gaps in current knowledge and the need for further research 3.

Disease Origin Spectrum

• Some peritoneal cancers are considered primary when no other origin is found, while others may be reclassified as metastatic after further investigation 1, 2, 5.

Treatment of Primary Peritoneal Cancer

Treatment of primary peritoneal cancer is complex and often mirrors strategies used for advanced ovarian cancer. Advances in surgery, chemotherapy, and targeted therapies have improved outcomes for selected patients, but prognosis depends on tumor type, stage, and overall health.

Treatment Modality	Description	Indication/Notes	Source(s)
Cytoreductive surgery	Surgical removal of tumor and affected tissue	Mainstay for operable disease	1, 4, 3, 8
Systemic chemotherapy	Platinum-based regimens (carboplatin/paclitaxel)	Standard for serous carcinoma	6, 4
HIPEC (intraperitoneal chemo)	Heated chemo delivered during surgery	Select cases, ongoing research	8, 9
Targeted therapies	PARP inhibitors, biologics	Under investigation	3
Palliative care	Symptom management	For advanced/untreatable disease	1, 8

Table 4: Main Treatment Options

Surgical Approaches

• Cytoreductive surgery (CRS) aims to remove as much visible tumor as possible. The extent of surgical resection (completeness of cytoreduction) is a key prognostic factor—the less residual disease, the better the outcome 1, 3, 4, 8.
• In some cases, surgery includes removal of the omentum, portions of bowel, reproductive organs, or other involved tissues 1, 6.

Chemotherapy

• Systemic chemotherapy—often platinum-based (carboplatin and paclitaxel)—is standard for serous carcinoma and other epithelial types 4, 6.
• Chemotherapy can be used before surgery (neoadjuvant) to shrink tumors or after (adjuvant) to reduce recurrence risk 4.
• For rare subtypes like clear cell carcinoma, similar regimens are used, although evidence is limited 6.

Hyperthermic Intraperitoneal Chemotherapy (HIPEC)

• HIPEC involves circulating heated chemotherapy drugs inside the abdomen during surgery. It is being studied for PPC and other peritoneal cancers, with some evidence of benefit in selected cases 8, 9.
• Guidelines currently recommend HIPEC mainly within clinical trials or specialized centers due to insufficient evidence for routine use 9.

Targeted and Novel Therapies

• Targeted therapies such as PARP inhibitors and anti-angiogenic agents are under investigation, especially for tumors with specific genetic mutations 3.
• Immunotherapy and nanomedicine are emerging areas of research, aiming to improve tumor targeting and reduce side effects 3.

Palliative and Supportive Care

• For advanced disease not amenable to curative treatment, palliative care focuses on symptom control—managing ascites, pain, and gastrointestinal symptoms to maintain quality of life 1, 8.
• Multidisciplinary support, including nutrition, pain management, and psychological care, is essential.

Conclusion

Primary peritoneal cancer remains a challenging diagnosis, but advances in understanding and treatment are improving patient outcomes. Key points include:

• Symptoms are often vague and overlap with other abdominal conditions, leading to delayed diagnosis.
• There are several types of PPC, with serous carcinoma being the most common; rare forms exist and require specialized diagnosis.
• Causes include malignant transformation of the peritoneal lining, environmental exposures (like asbestos), and genetic factors, but many cases remain unexplained.
• Treatment is multidisciplinary, typically combining surgery and chemotherapy, with HIPEC and targeted therapies as emerging options.
• Early detection and optimal cytoreduction are crucial for improving survival and quality of life.

Staying informed and seeking care from specialized, multidisciplinary teams can make a significant difference for those facing primary peritoneal cancer.