Groupings, Grades and Subtypes of Ovarian Cancer

Reviewed by: HU Medical Review Board | Last reviewed: May 2021

Along with staging ovarian cancer, doctors further break it down into subtypes, grades, and groupings. This helps guide treatment and prognosis. Knowing more about how your cancer is categorized can help you make informed decisions about your treatment.

If you have questions about your stage, grouping, or subtype, talk with your doctor. They will be able to give you more details about your cancer and what it means for your treatment plan.

What are the groupings in the stages?

There are different ways to stage ovarian cancer, but they generally overlap and can be used together. The 2 systems include the International Federation of Gynecology and Obstetrics (FIGO) system and the American Joint Committee on Cancer (AJCC) system.1

There are groups that fall under the stages outlined in the FIGO and AJCC staging systems. The groups help further to classify the extent of the spread of the cancer. The groupings include the TNM scoring system:1,2

  • T refers to the tumor and its size
  • N refers to whether adjacent or nearby lymph nodes have cancer
  • M refers to any metastases (cancer spread to other distant areas of the body)

Doctors use numbers and letters after the T, N, or M to reflect the spread of the cancer.1,2

These groupings within the stages can be confusing, so they are not often used outside of clinical settings. If you have any questions about groupings and stages of ovarian cancer, ask your doctor what they mean for your specific disease stage.

Ovarian cancer stages and groupings

The stages and groupings include:1

  • Stage I
    • T1, N0, M0
  • Stage IA
    • T1a, N0, M0
  • Stage IB
    • T1b, N0, M0
  • Stage IC
    • T1c, N0, M0
  • Stage II
    • T2, N0, M0
  • Stage IIA
    • T2a, N0, M0
  • Stage IIB
    • T2b, N0, M0
  • Stage IIIA1
    • T1 or T2, N1, M0
  • Stage IIIA2
    • T3a, N0 or N1, M0
  • Stage IIIB
    • T3b, N0 or N1, M0
  • Stage IIIC
    • T3c, N0 or N1, M0
  • Stage IVA
    • Any T, any N, M1a
  • Stage IVB
    • Any T, any N, M1b

Sometimes you will also see the following AJCC stages used:1

  • TX – The main tumor cannot be properly assessed because of a lack of information
  • T0 – There is no evidence of a primary tumor
  • NX – The regional lymph nodes cannot be assessed because there is not enough information

What are the grades in ovarian cancer?

Along with stages of cancer, there are also tumor grades. These are not the same as stages.

Grade, known as G, refers to how the cells look under a microscope. If the cancer looks similar to healthy tissue with various cell groupings, it is described as a low-grade tumor, or differentiated. If the cancer looks very different from healthy tissue, it is called high-grade, or poorly differentiated.3

The tumor grade may help predict how quickly the cancer will grow or spread. It can also be a factor in treatment decisions.3

Tumor grades are described by the following:3

  • GX – The grade cannot be evaluated
  • GB – The tissue is thought to be borderline cancerous; this is commonly called low malignant potential (LPM)
  • G1 – Tissue is well-differentiated, with a lot of healthy-looking cells
  • G2 – Tissue is moderately differentiated; more cells look abnormal than healthy
  • G3 to G4 – Tissue is poorly differentiated or undifferentiated; many cells look abnormal and do not have normal tissue structures

What are the types and subtypes of ovarian cancer?

Within ovarian cancer, there are different types and subtypes of disease. There are more than 30 different specific types, but most are identified by the name of the cell from which the cancer started.4

The most common type of ovarian cancers start in the epithelial cells, on the outer layer of the ovary. Ovarian cancer may also start in the germ cells, which make eggs, or in the stromal cells, which make hormones.4

Epithelial ovarian cancers

Epithelial ovarian cancers make up about 85 to 90 percent of ovarian cancers, even though most epithelial tumors are benign, or non-cancerous. They start in the cells on the surface of the ovary.1,4

There are generally 4 subtypes of epithelial ovarian cancer:5

  • Mucinous
  • Endometrioid
  • Clear cell
  • Serous

High-grade serous epithelial ovarian carcinoma is the most common type of invasive epithelial ovarian cancer.5

Ovarian germ cell tumors

Ovarian germ cell tumors start from the cells that produce the eggs. Most are not cancerous. The most common germ cell cancers include:3

  • Malignant teratomas
  • Dysgerminomas
  • Endodermal sinus tumors

These most often occur in teenagers and women in their 20s. About 90 percent of these germ cell ovarian cancers can be cured while also preserving fertility.3

Ovarian stromal tumors

Ovarian stromal tumors are rare and stem from the connective tissue cells that hold the ovaries together. These cells also produce the hormones estrogen and progesterone. The most common types of these tumors are granulosa-theca tumors and Sertoli-Leydig cell tumors.3

In addition to being rare, they are also typically low-grade, with about 70 percent of cases found in stage I.3

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