Mucinous Ovarian Tumours and Pseudomyxoma Peritonei

Prepared and reviewed by the PrepElephant Academic Review Team

First published 8 Oct 2026 · Spot an error?

Reference basis: Williams Gynecology; WHO Classification of Female Genital Tumours; Shaw's Textbook of Gynaecology

On this page

Direct answer
What you must remember
Separating ovarian and appendiceal origin
Mucinous traps in the exam
Frequently asked questions
Related topics

Direct answer

Mucinous ovarian tumours are epithelial neoplasms lined by intestinal-type cells that secrete mucin, and primary tumours are usually unilateral. Pseudomyxoma peritonei is a condition of mucin accumulation in the abdomen, producing gelatinous ascites and implants, and it most often arises from an appendiceal primary rather than the ovary. Diagnosis rests on histology, appendix assessment and immunohistochemistry to separate ovarian from gastrointestinal origin.

What you must remember

Histology: tall columnar mucinous cells with basal nuclei, apical mucin and goblet cells, resembling intestinal epithelium.
Laterality: primary mucinous tumours are usually unilateral, whereas bilateral disease suggests metastasis, such as a Krukenberg tumour.
Spectrum: cystadenomas, borderline tumours and carcinomas differ by epithelial atypia and, for carcinoma, stromal invasion.
Pseudomyxoma peritonei: mucin accumulates in the peritoneal cavity, producing gelatinous ascites and implants on the peritoneal surfaces.
Appendix: an appendiceal mucinous neoplasm is the commonest primary of pseudomyxoma, so the appendix must be examined and removed when involved.
Immunohistochemistry: CDX2 and CK20 favour a gastrointestinal origin, while CK7 positivity with CK20 negativity is more typical of ovarian origin.
Markers: CEA and CA 19-9 are often raised in mucinous disease, but neither is specific.
Treatment: cytoreductive surgery with hyperthermic intraperitoneal chemotherapy is used for pseudomyxoma in specialist centres.

Separating ovarian and appendiceal origin

Mucinous disease is a diagnostic problem before it is a surgical one, because the primary site decides the treatment. The appendix and the ovaries must be assessed together, because each can harbour the primary.

Histology first: Confirm that the tumour is mucinous and grade it as benign, borderline or malignant by stromal invasion and architecture. Benign and borderline tumours are managed differently from invasive carcinoma.
Examine the appendix: Inspect the appendix at laparotomy, since a mucocele or abnormal appendix suggests an appendiceal primary. An appendicectomy is reasonable when the appendix is abnormal.
Map the spread: Note laterality, gelatinous ascites, peritoneal implants and whether the disease is confined to the pelvis. Peritoneal spread with gelatinous ascites points towards pseudomyxoma rather than a solid carcinoma.
Immunohistochemistry: Use CK7, CK20 and CDX2 together, interpreting the panel as a whole rather than any single stain. A mixed profile should prompt a return to imaging and endoscopy.
Plan the surgery: Remove the ovarian disease and any abnormal appendix, and refer pseudomyxoma for cytoreduction, often with hyperthermic intraperitoneal chemotherapy in a specialist unit.

Mucinous traps in the exam

Mucinous questions reward distinguishing ovarian from metastatic disease and recognising pseudomyxoma.

Trap: Calling bilateral mucinous ovarian disease primary by default Correct: bilateral involvement suggests metastasis from a gastrointestinal source, so a primary must be sought.
Trap: Removing the ovary and ignoring the appendix in pseudomyxoma Correct: the appendix is the commonest primary, so it must be examined and managed.
Trap: Describing pseudomyxoma as a benign condition Correct: it is often low grade but can progress, and mucin accumulation can cause intestinal obstruction.
Trap: Using CEA alone to decide the origin Correct: CEA is raised in many mucinous tumours, so it must be read with immunohistochemistry and imaging.

Frequently asked questions

How can an ovarian mucinous tumour be distinguished from an appendiceal primary?

Examine the appendix at surgery and use immunohistochemistry, since an appendiceal primary often spreads to the ovary. CDX2 and CK20 favour gastrointestinal origin, while a CK7-positive, CK20-negative profile is more typical of an ovarian primary.

What is pseudomyxoma peritonei?

Pseudomyxoma peritonei is accumulation of mucin in the peritoneal cavity, producing gelatinous ascites and peritoneal implants. Most cases arise from an appendiceal mucinous neoplasm rather than the ovary, so the appendix must be assessed.

Why is bilateral mucinous ovarian disease suspicious for metastasis?

Primary mucinous ovarian tumours are usually unilateral, so bilateral disease raises suspicion of metastasis, most often from a gastrointestinal primary such as the stomach or appendix. Evaluation of the primary site is therefore essential before deciding treatment.

What surgery treats pseudomyxoma peritonei?

Cytoreductive surgery to remove visible mucinous disease is the mainstay, often combined with hyperthermic intraperitoneal chemotherapy in specialist centres. Repeat surgery may be needed because the disease tends to recur.