Understanding Tumors

Normally cells divide only when additional cells are required for normal body function. However, at certain times the controls that regulate when a cell divides are lost. This results in accumulation of more and more cells without order. Eventually these cells grow into a mass and this is termed a 'tumor'. It is important to understand that not all tumors are cancer.

normal ovary

Types of Ovarian Cancer

There are three main types of ovarian tumors:

  • Epithelial tumors- derived from the cells on the surface of the ovary. This is the most common form of ovarian cancer and occurs primarily in adults.
  • Germ cell tumors- derived from the egg producing cells within the body of the ovary. This occurs primarily in children and teens and is rare by comparison to epithelial ovarian tumors.
  • Stromal tumors - rare in comparison to epithelial tumors and this class of tumors often produces steroid hormones.

Under the Microscope: Epithelial Ovarian Tumors

  • High-Grade Serous Carcinoma Epithelial Ovarian Tumor

    High-grade serous carcinoma (HGSC)

    The most frequent and most lethal gynecologic cancer. HGSC is diagnosed at advanced stages in ~70% of cases, and have a significantly worse outcome than those with early stage disease.

  • Ovarian Endometrioid Carcinoma Epithelial Tumor

    Ovarian endometrioid carcinoma

    Representing the second most common form of ovarian epithelial malignancy. The frequent association of ovarian endometrioid carcinomas with endometriosis, endometrial carcinoma or both suggests that some may share risk factors with endometrial carcinomas.

  • Clear Cell Carcinoma Epithelial Tumor

    Clear cell carcinoma

    A malignant tumor composed of clear, eosinophilic and hobnail cells, displaying a combination of tubulocystic, papillary and solid patterns. CCC in the ovary is most frequently associated with ovarian or pelvic endometriosis.

  • Mucinous Carcinoma Epithelial Tumor

    Mucinous carcinoma

    A malignant epithelial tumor composed of gastrointestinal-type cells. Mucinous carcinoma accounts for 3-4% of all primary ovarian carcinomas. Most tumors are confined to the ovary at presentation. Advanced stage primary mucinous ovarian carcinoma is rare.

  • Low-Grade Serous Carcinoma Epithelial Tumor

    Low-grade serous carcinomas (LGSCs)

    These account for about 5% of all serous carcinomas. LGSCs do not respond well, but are not refractory to, conventional platinum-based chemotherapy in the neoadjuvant, adjuvant or recurrent settings. These tumors may respond to hormone therapy.

Under the Microscope: Epithelial Ovarian Tumors

High-grade serous carcinoma (HGSC)

The most frequent and most lethal gynecologic cancer. HGSC is diagnosed at advanced stages in ~70% of cases, and have a significantly worse outcome than those with early stage disease.


Ovarian endometrioid carcinoma

Representing the second most common form of ovarian epithelial malignancy. The frequent association of ovarian endometrioid carcinomas with endometriosis, endometrial carcinoma or both suggests that some may share risk factors with endometrial carcinomas.


Clear cell carcinoma

A malignant tumor composed of clear, eosinophilic and hobnail cells, displaying a combination of tubulocystic, papillary and solid patterns. CCC in the ovary is most frequently associated with ovarian or pelvic endometriosis.


Mucinous carcinoma

A malignant epithelial tumor composed of gastrointestinal-type cells. Mucinous carcinoma accounts for 3-4% of all primary ovarian carcinomas. Most tumors are confined to the ovary at presentation. Advanced stage primary mucinous ovarian carcinoma is rare.


Low-grade serous carcinomas (LGSCs)

These account for about 5% of all serous carcinomas. LGSCs do not respond well, but are not refractory to, conventional platinum-based chemotherapy in the neoadjuvant, adjuvant or recurrent settings. These tumors may respond to hormone therapy.


Under the Microscope: Germ Cell Ovarian Tumors

  • Dysgerminoma Germ Cell Ovarian Tumor

    Dysgerminoma

    A primitive germ cell tumor composed of cells showing no specific pattern of differentiation. Most common malignant cell tumor of the ovary, but comprises only 1-2% of all malignant ovarian tumors.

  • Yolk Sac Germ Cell Ovarian Tumor

    Yolk sac tumor

    A primitive germ cell tumor with a variety of distinctive patterns which may also exhibit differentiation into endodermal structures, ranging from the primitive gut and mesenchyme to the derivatives of extra-embryonal and embryonal somatic tissues.

Under the Microscope: Germ Cell Ovarian Tumors

Dysgerminoma

A primitive germ cell tumor composed of cells showing no specific pattern of differentiation. Most common malignant cell tumor of the ovary, but comprises only 1-2% of all malignant ovarian tumors.


Yolk sac tumor

A primitive germ cell tumor with a variety of distinctive patterns which may also exhibit differentiation into endodermal structures, ranging from the primitive gut and mesenchyme to the derivatives of extra-embryonal and embryonal somatic tissues.


Under the Microscope: Sex Cord Stromal Ovarian Tumors

  • Adult Granulosa Cell Ovarian Tumor

    Adult granulosa cell tumor

    A low-grade malignant, sex cord-stromal tumor with a variable number of fibroblasts and theca cells. A variety of growth patterns occur and are often admixed. Adult granulosa cell tumor accounts for about 1% of all ovarian tumors.

  • Sertoli-Leydig Cell Ovarian Tumor

    Sertoli-Leydig cell tumors

    Composed of variable proportions of Sertoli cells, Leydig cells and in the case of moderately and poorly differentiated neoplasms, primitive gonadal stroma and sometimes heterologous elements. These are rare, accounting for < 0.5% of ovarian neoplasms.

Under the Microscope: Sex Cord Stromal Ovarian Tumors

Adult granulosa cell tumor

A low-grade malignant, sex cord-stromal tumor with a variable number of fibroblasts and theca cells. A variety of growth patterns occur and are often admixed. Adult granulosa cell tumor accounts for about 1% of all ovarian tumors.


Sertoli-Leydig cell tumors

Composed of variable proportions of Sertoli cells, Leydig cells and in the case of moderately and poorly differentiated neoplasms, primitive gonadal stroma and sometimes heterologous elements. These are rare, accounting for < 0.5% of ovarian neoplasms.