Pseudomyxoma peritonei
Updates to Article Attributes
Pseudomyxoma peritonei refers to thesyndrome of progressive intraperitoneal accumulation of a gelatinousmucinous ascites secondaryrelated to rupture of a mucinous tumourmucin-producing neoplasm. TheIt is most common cause iscommonly caused by a ruptured mucinous tumour of the appendix/appendiceal mucocoele
OccasionallyMuch less commonly, mucinous mucinous tumours of the colon, rectum, stomach, pancreas , and urachal tumoursurachus 9,10,13 are implicated. There is some ongoing contention as to whether primary ovarian tumours are a frequent source in their own right, or whether in these cases the appendix is the primary site and the ovarian lesion is metastatic 2,3.
Terminology
The terminology regarding pseudomyxoma peritonei can be a bit confusing, and continues to evolve over time. In 2016, a consensus group, the Peritoneal Surface Oncology Group International, published guidelines for classification for mucinous appendiceal tumors and associated peritoneal disease (see appendiceal mucinous neoplasm article).
An "appendiceal mucocele" is a descriptive term which refers to the appearance of a dilated mucin-filled appendix. Although this is the imaging manifestation of appendiceal mucinous tumors, appendiceal mucoceles may also represent non-neoplastic etiologies such as mucosal hyperplasia or retention cyst related to luminal obstruction 14.
Pathology
Pseudomyxoma peritonei (of appendiceal origin) is due to invasion or rupture of the appendix from a mucin-secreting appendiceal tumor.
It is important to understand that pseudomyxoma peritonei represents a spectrum of disease. The characteristic mucinous ascites is composed of acellular mucin and a variable amount of neoplastic epithelial cells. Indeed, pseudomyxoma peritonei is not a histologic diagnosis - the label merely implies grossly mucinous intraperitoneal deposits 15.
The remarkable feature of pseudomyxoma peritonei is that this neoplastic, progressive process often arises from a seemingly benign or well-differentiated primary tumour 3. With the rupture of these mucinous tumoursHowever once there is intraperitoneal spread, the mucus and cells will flow along with themucinous deposits tend to follow routes of normal peritoneal fluid and spread with deposits commonly seen atflow, spreading along the pelvis, paracolic gutters, on the liver capsule, and on the omentumomentum, while often sparing mobiel organs, e.g. small bowel 13, 14.
Pseudomyxoma peritonei may be divided into two pathological subtypes which have aetiological and prognostic significance 4:
-
peritoneal adenomucinosis
- a peritoneal neoplasm composed largely of mucin associated with fibrosis with minimal cytological atypia and mitoses
- the primary tumour is generally an adenoma
-
peritoneal mucinous carcinoma
- characterised by proliferative epithelium, glands, nests, or individual cells with marked cytologic atypia
- the primary is a mucinous adenocarcinoma
Not all cases fit neatly into these categories, and many patients have intermediate or discordant features.
However, a long term follow-up study 4 of 109 patients found 5-year survival rates were markedly different: 75% for the adenomucinosis group and 14% for the mucinous carcinoma group. The intermediate/discordant group 5 year survival was 50%.
Radiographic features
ItPseudomyxoma peritonei is typically characterised by loculated collections of fluid causing scallopingwhich accumulate along peritoneal surfaces, classically resulting in a scalloped appearance of abdominopelviccoated abdominal organs and omental caking. An appendiceal mucocele (representing an mucinous appendiceal tumor) may be visualized.
- since appendiceal tumors are most common etiology, early peritoneal disease may be limited to the right lower quadrant abdomen 15
- deposits tend to localize to site of physiologic lymphatic absorption of ascites (omentum, underneath right hemidiaphragm), and dependent areas (e.g. paracolic gutters, right retrohepatic space, lower pelvis) 14
- deposits tend to spare the more mobile small bowel until later in disease, when it eventually causes bowel obstruction14
Plain radiograph
May show evidence of ascites with centrally displaced small bowel loops and scattered punctate or curvilinear calcifications.
Ultrasound
- echogenic peritoneal masses or ascites with echogenic particles which (unlike other forms of particulate ascites such as haemoperitoneum or pus in the peritoneum) do not move 6
- small bowel loops displaced medially
- may show scalloping of the liver, spleen and at times other organs
CT
-
simple or loculated low attenuation
, often loculatedfluid throughoutthe peritoneumintraperitoneal spaces, omentum, and mesentery14 - scalloping of visceral surfaces, particularly the liver 5
-
often with scattered (curvilinear or punctate) calcifications
may be frequently present5 - tends to remain localised to
theperitoneal cavity - thoracic and nodal lesions metastases uncommon
MRI
Reported signal characteristics of the collections include 8
- T1: typically low signal
- T2: typically high signal
- T1 C+ (Gd): may show enhancement 12
Treatment and prognosis
This is a progressive and often fatal disease. Recurrent bowel obstructions are commonly due to the fibrosis and adhesions in advanced disease 13.
Treatment is surgical debulking, followed by infusion of intraperitoneal chemotherapy. Aggressive surgical treatment has been considered based on the calculation of the peritoneal cancer index (PCI), which is a prognostic indicator based on the amount of tumour found at laparoscopy. This index has been performed using CT or MRI 13.
Differential diagnosis
General imaging differential considerations include:
- peritoneal carcinomatosis without mucinous ascites
- peritoneal sarcomatosis 2
- peritonitis
-<p><strong>Pseudomyxoma peritonei </strong>refers to the intraperitoneal accumulation of a gelatinous ascites secondary to rupture of a mucinous tumour. The most common cause is a ruptured <a href="/articles/mucinous-neoplasms-of-the-appendix">mucinous tumour of the appendix</a>/<a href="/articles/appendiceal-mucocele-2">appendiceal mucocoele</a> <sup>10</sup>. </p><p>Occasionally, mucinous tumours of the colon, rectum, stomach, pancreas and urachal tumours <sup>9,10,13</sup> are implicated. There is some ongoing contention as to whether primary ovarian tumours are a frequent source in their own right, or whether in these cases the appendix is the primary site and the ovarian lesion is metastatic <sup>2,3</sup>.</p><h4>Pathology</h4><p>The remarkable feature of pseudomyxoma peritonei is that this neoplastic, progressive process often arises from a seemingly benign or well-differentiated primary tumour <sup>3</sup>. With the rupture of these mucinous tumours, the mucus and cells will flow along with the peritoneal fluid and spread with deposits commonly seen at the pelvis, paracolic gutters, on the liver capsule, and on the omentum <sup>13</sup>. </p><p>Pseudomyxoma peritonei may be divided into two pathological subtypes which have aetiological and prognostic significance <sup>4</sup>:</p><ul>- +<p><strong>Pseudomyxoma peritonei </strong>refers to syndrome of progressive intraperitoneal accumulation of mucinous ascites related to a mucin-producing neoplasm. It is most commonly caused by a <a href="/articles/mucinous-neoplasms-of-the-appendix">mucinous tumour of the appendix</a> <sup>10</sup>.</p><p>Much less commonly, mucinous tumours of colon, rectum, stomach, pancreas , and urachus <sup>9,10,13</sup> are implicated. There is some ongoing contention as to whether primary ovarian tumours are a frequent source in their own right, or whether in these cases the appendix is the primary site and the ovarian lesion is metastatic <sup>2,3</sup>.</p><h4>Terminology</h4><p>The terminology regarding pseudomyxoma peritonei can be a bit confusing, and continues to evolve over time. In 2016, a consensus group, the Peritoneal Surface Oncology Group International, published guidelines for classification for mucinous appendiceal tumors and associated peritoneal disease (see <a href="/articles/mucinous-neoplasms-of-the-appendix">appendiceal mucinous neoplasm article</a>).</p><p>An <a href="/articles/appendiceal-mucocele-2">"appendiceal mucocele"</a> is a descriptive term which refers to the appearance of a dilated mucin-filled appendix. Although this is the imaging manifestation of appendiceal mucinous tumors, appendiceal mucoceles may also represent non-neoplastic etiologies such as mucosal hyperplasia or retention cyst related to luminal obstruction <sup>14</sup>.</p><h4>Pathology</h4><p>Pseudomyxoma peritonei (of appendiceal origin) is due to invasion or rupture of the appendix from a mucin-secreting appendiceal tumor.</p><p>It is important to understand that pseudomyxoma peritonei represents a spectrum of disease. The characteristic mucinous ascites is composed of acellular mucin and a variable amount of neoplastic epithelial cells. Indeed, pseudomyxoma peritonei is not a histologic diagnosis - the label merely implies grossly mucinous intraperitoneal deposits <sup>15</sup>.</p><p>The remarkable feature of pseudomyxoma peritonei is that this neoplastic, progressive process often arises from a seemingly benign or well-differentiated primary tumour <sup>3</sup>. However once there is intraperitoneal spread, the mucinous deposits tend to follow routes of normal peritoneal fluid flow, spreading along the pelvis, paracolic gutters, liver capsule, and omentum, while often sparing mobiel organs, e.g. small bowel <sup>13, 14</sup>. </p><p>Pseudomyxoma peritonei may be divided into two pathological subtypes which have aetiological and prognostic significance <sup>4</sup>:</p><ul>
-</ul><p>Not all cases fit neatly into these categories, and many patients have intermediate or discordant features. </p><p>However, a long term follow-up study <sup>4</sup> of 109 patients found 5-year survival rates were markedly different: 75% for the adenomucinosis group and 14% for the mucinous carcinoma group. The intermediate/discordant group 5 year survival was 50%.</p><h4>Radiographic features</h4><p>It is typically characterised by loculated collections of fluid causing scalloping of abdominopelvic organs.</p><h5>Plain radiograph</h5><p>May show evidence of ascites with centrally displaced small bowel loops and scattered punctate or curvilinear calcifications.</p><h5>Ultrasound </h5><ul>- +</ul><p>Not all cases fit neatly into these categories, and many patients have intermediate or discordant features. </p><p>However, a long term follow-up study <sup>4</sup> of 109 patients found 5-year survival rates were markedly different: 75% for the adenomucinosis group and 14% for the mucinous carcinoma group. The intermediate/discordant group 5 year survival was 50%.</p><h4>Radiographic features</h4><p>Pseudomyxoma peritonei is characterised by loculated collections of fluid which accumulate along peritoneal surfaces, classically resulting in a scalloped appearance of coated abdominal organs and omental caking. An appendiceal mucocele (representing an mucinous appendiceal tumor) may be visualized.</p><ul>
- +<li>since appendiceal tumors are most common etiology, early peritoneal disease may be limited to the right lower quadrant abdomen <sup>15</sup>
- +</li>
- +<li>deposits tend to localize to site of physiologic lymphatic absorption of ascites (omentum, underneath right hemidiaphragm), and dependent areas (e.g. paracolic gutters, right retrohepatic space, lower pelvis) <sup>14</sup>
- +</li>
- +<li>
- +<span style="font-size:10.8333px">d</span>eposits tend to spare the more mobile small bowel until later in disease, when it eventually causes <a href="/articles/bowel-obstruction">bowel obstruction</a> <sup>14</sup>
- +</li>
- +</ul><h5>Plain radiograph</h5><p>May show evidence of ascites with centrally displaced small bowel loops and scattered punctate or curvilinear calcifications.</p><h5>Ultrasound </h5><ul>
-<li>low attenuation, often loculated fluid throughout the peritoneum, omentum and mesentery</li>- +<li>simple or loculated low attenuation fluid throughout intraperitoneal spaces, omentum, and mesentery <sup>14</sup>
- +</li>
-<li>scattered (curvilinear or punctate) calcifications may be frequently present <sup>5</sup>- +<li>often with scattered (curvilinear or punctate) calcifications <sup>5</sup>
-<li>tends to remain localised to the peritoneal cavity</li>- +<li>tends to remain localised to peritoneal cavity - thoracic and nodal lesions metastases uncommon</li>
References changed:
- 14. Bartlett DJ, Thacker PG, Grotz TE et-al. Mucinous appendiceal neoplasms: classification, imaging, and HIPEC. (2019) Abdominal Radiology. <a href="https://doi.org/10.1007/s00261-018-01888-y">doi:10.1007/s00261-018-01888-y</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/30610247">Pubmed</a> <span class="ref_v4"></span>
- 15. Legué LM, Creemers GJ, de Hingh IHJT et-al. Review: Pathology and Its Clinical Relevance of Mucinous Appendiceal Neoplasms and Pseudomyxoma Peritonei. (2018) Clinical colorectal cancer. <a href="https://doi.org/10.1016/j.clcc.2018.11.007">doi:10.1016/j.clcc.2018.11.007</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/30611664">Pubmed</a> <span class="ref_v4"></span>
Unable to process the form. Check for errors and try again.