Peritoneal tumours
How the peritoneum’s mesothelium and circulating fluid shape its tumours: peritoneal mesothelioma, primary peritoneal serous carcinoma, pseudomyxoma from appendiceal mucinous neoplasms, and carcinomatosis with malignant ascites.
By the end, you can
- Describe the peritoneum, the flow of peritoneal fluid and why free tumour cells settle in the omentum, pelvis and under the right diaphragm.
- Compare peritoneal mesothelioma with primary peritoneal serous carcinoma by origin, microscopy and markers.
- Explain how a low-grade appendiceal mucinous neoplasm leads to pseudomyxoma peritonei and why its grade guides behaviour.
- Explain how peritoneal carcinomatosis from the ovary, stomach and colon causes malignant ascites and bowel obstruction.
- Explain why peritoneal spread is staged differently for gastrointestinal and ovarian cancers.
- Recognise the classic appearances, classifications and tests of peritoneal tumours, and explain how cytoreductive surgery with heated intraperitoneal chemotherapy, systemic treatment and drainage act on them.
What it is
Peritoneal tumours involve the lining of the abdominal cavity. Primary tumours are rare: peritoneal mesothelioma (from mesothelial cells) and primary peritoneal serous carcinoma (a Müllerian-type carcinoma in women). Pseudomyxoma peritonei is mucinous tumour filling the cavity, almost always from the appendix. Most peritoneal malignancy is secondary: carcinomatosis from the ovary, stomach, colon and pancreas.
4 types to tell apart
- Peritoneal mesothelioma
- Malignant mesothelial tumour coating the peritoneum, mostly epithelioid; less tied to asbestos than pleural mesothelioma.
- Primary peritoneal serous carcinoma
- High-grade serous carcinoma of the peritoneum with normal-sized ovaries; linked to BRCA mutations; behaves like ovarian high-grade serous carcinoma.
- Pseudomyxoma peritonei
- Mucin and mucinous tumour cells filling the cavity, usually from a low-grade appendiceal mucinous neoplasm; graded low or high.
- Peritoneal carcinomatosis
- Secondary carcinoma spread across the peritoneum, mainly from ovary, stomach, colon, appendix and pancreas, with malignant ascites.
US spelling: tumours → tumors, tumour → tumor.
Normal function
The peritoneum and its circulating fluid
The peritoneum lines the abdominal wall (parietal peritoneum) and covers the organs (visceral peritoneum), folding into the mesenteries and the , an apron of fat hanging from the over the bowel. Its surface is the same mesothelium that lines the pleura, with the same cell features and markers (see the pleural tumours lesson). In women the cavity opens into the uterine tubes, and the ovaries lie within it.
A small volume of fluid lubricates the surfaces. Breathing and bowel movement keep it circulating: it pools in the pelvis, flows up the right paracolic gutter to the underside of the right hemidiaphragm, beside the , and drains there through lymphatic stomata towards mediastinal nodes. The omentum also absorbs fluid and particles through milky spots, clusters of macrophages and lymphocytes. Free cells in the cavity follow this flow and settle where fluid is absorbed or pools.
In women, the mesothelium and the cells beneath it can take on Müllerian (tubal or endometrial) features, as in endometriosis, so carcinomas like those of the tube and ovary can also arise in the peritoneum.
Underlying change · Step 1 of 4
Peritoneal mesothelioma: the same cell, a different cavity
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Underlying change · Step 2 of 4
Primary peritoneal serous carcinoma: a tubal-type cancer outside the tube
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Disrupted function · Step 3 of 4
Pseudomyxoma peritonei: mucin from the appendix
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Consequences · Step 4 of 4
Peritoneal carcinomatosis and malignant ascites
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Symptoms and signs
Symptoms, signs and findings
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Exam detail
Exam detail
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Treatment
How treatment works
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Recap
Recap
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Self-check
Check your understanding
The full lesson is part of Student Pro
It takes you through all 4 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 10 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .