Ovarian epithelial tumors account for the majority of all ovarian tumors (60-70%) and their malignant forms represent >90% of ovarian cancers ¹. They can range from benign to highly malignant tumors.

Epidemiology

There is a difference in the frequency of ovarian tumor subtypes depending on menopausal status ⁶:

• premenopausal

  • serous (~60%)

  • mucinous (~20%)

  • endometrioid (~10%)

  • clear cell  (~5%)

  • other (~5%)

• postmenopausal

  • serous (~60%)

  • endometrioid (~12.5%)

  • clear cell (~10%)

  • mucinous (~7.5%)

  • other (~10%)

Pathology

The origin and pathogenesis of epithelial ovarian cancer are poorly understood ⁵. Despite extensive studies, no precursor lesions have been found ⁵.

Classification

Ovarian epithelial tumors are histologically classified according to:

1. resemblance to normal gynecological cell line ⁷

   • serous: resembling epithelium lining the Fallopian tubes

   • mucinous: resembling epithelium lining endocervix, containing intracytoplasmic mucin

   • endometrioid: resembling epithelium/stroma of uterine corpus

   • clear cell: comprising clear cells and hobnail cells

2. grade of aggressiveness ^7,8

   • several grading systems exist, and grading may differ according to histologic type

   • e.g. three-tier FIGO system, two-tier MDACC system for serous tumors

A more complete list of ovarian epithelial tumors is as follows:

• ovarian serous tumors

  • ovarian serous cystadenoma: ~60% of serous tumors  

  • ovarian borderline serous cystadenoma:  ~15% of serous tumors

  • ovarian serous cystadenocarcinoma: ~25% of serous tumors (most common malignant ovarian tumor)

• ovarian mucinous tumors: ~20% of all ovarian tumors 

  • ovarian mucinous cystadenoma: ~80% of mucinous tumors

  • ovarian borderline mucinous cystadenoma: 10-15% of mucinous tumors

  • ovarian mucinous cystadenocarcinoma: ~5-10% of mucinous tumors

• ovarian endometrioid tumor: 8-15% of all ovarian tumors

• ovarian cystadenofibroma* / ovarian adenofibroma: can be serous, mucinous, endometrioid, clear cell, or mixed

• ovarian cystadenocarcinofibroma: extremely rare

• clear cell ovarian carcinoma: ~5% of ovarian cancer

• Brenner tumor: 2-3% of ovarian epithelial neoplasms

• undifferentiated carcinoma of the ovary: ~4% of all ovarian tumors

• squamous cell carcinoma of the ovary

* sometimes classified as a separate category rather than under epithelial 

Markers

• elevation of serum CA-125 levels

• human epididymis protein 4 (HE4)

Radiographic features

These can range from being cystic, to solid, to anything in between. As a crude rule, the likelihood of malignancy increases with increasing solid-tissue elements and thicker septae ². While there are some common features, there are also many variations and it may be best to refer to subarticles for specific imaging features.