Epithelial ovarian tumors overview
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Epithelial ovarian tumors Microchapters |
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Differentiating Epithelial Ovarian Tumors from other Diseases |
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Diagnosis |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Hannan Javed, M.D.[2]Huda A. Karman, M.D.
Overview
Ovarian cancer was first linked to gene mutations by Dr. King who found and named BRCA1 gene on chromosome 17 in 1990 and BRCA2 gene on chromosome 13 in 1994. Ovarian epithelial tumors can be classified on several bases depending on the morphology, histopathological behavior and clinical characteristics. The general classification of benign, borderline and malignant tumors is supplemented by classification systems augmented by molecular and clinico-pathological behavior of the tumors. This section also contains WHO classification of ovarian tumors to allow differentiation between epithelial tumors and other ovarian tumors. Surface epithelium of ovaries (OSE), once mistakenly referred as germinal epithelium, consists of single layer of flat to cuboidal epithelial cells. It is characterized by keratin types found in simple epithelium and functions in exchange between peritoneal cavity and the ovaries in addition to ovarian cycle. During embryonic development, surface epithelium of ovaries is a part of celomic epithelium. The future surface epithelium of ovaries then forms part of gonadal blastema and then undergoes a transformation cycle, multilayered papillary epithelium develops from simple flat to cuboidal epithelium but reverts back to simple flat to cuboidal epithelium by term. The most important functions of human surface epithelium of ovaries are its role in transport and exchange between peritoneal cavity and ovaries, and its function in repair and rupture during ovulation. Ovarian surface epithelium undergo epithelio-mesenchymal transformation to replace ovarian stroma in ovulatory repair. The previous proposition regarding the origin of epithelial ovarian cancers was that these tumors originated from surface epithelium of the ovaries and the neoplastic and metaplastic changes led to their differentiation into various histological subtypes such as serous tumors, clear cell carcinoma and endometrioid tumors. But apparent consistencies in this theory has led to development of alternate theories such as origin of neoplastic cells from fallopian tubes and endometrium. Epithelial ovarian tumors' etiology is not completely understood but there are multiple risk factors that can play a role in its occurrence. The theories of the etiology of ovarian cancer suggest that repeated ovulation injures the ovarian epithelium and eventually leads to ovarian cancer development. The other theories discuss the origin of ovarian cancer that can be cortical inclusion cysts that become neoplastic or metaplastic or dysplastic changes of the fallopian tube. Direct effect of persistent Gonadotrophin release from the pituitary gland on the ovary also believed to play a role in ovarian cancer etiology. On the basis of age of onset, vaginal discharge, and constitutional symptoms, ovarian cancer must be differentiated from tubo-ovarian abscess, ectopic pregnancy, hydrosalpinx, salpingitis, fallopian tube carcinoma, uterine leiomyoma, choriocarcinoma, leiomyosarcoma, pregnancy, appendiceal abscess, appendiceal neoplasm, diverticular abscess, colorectal cancer, pelvic kidney, advanced bladder cancer, and retroperitoneal sarcoma.
Historical Perspective
Ovarian cancer was first linked to gene mutations by Dr. King who found and named BRCA1 gene on chromosome 17 in 1990 and BRCA2 gene on chromosome 13 in 1994.
Classification
Ovarian epithelial tumors can be classified on several bases depending on the morphology, histopathological behavior and clinical characteristics. The general classification of benign, borderline and malignant tumors is supplemented by classification systems augmented by molecular and clinico-pathological behavior of the tumors. This section also contains WHO classification of ovarian tumors to allow differentiation between epithelial tumors and other ovarian tumors.
Pathophysiology
Surface epithelium of ovaries (OSE), once mistakenly referred as germinal epithelium, consists of single layer of flat to cuboidal epithelial cells. It is characterized by keratin types found in simple epithelium and functions in exchange between peritoneal cavity and the ovaries in addition to ovarian cycle. During embryonic development, surface epithelium of ovaries is a part of celomic epithelium. The future surface epithelium of ovaries then forms part of gonadal blastema and then undergoes a transformation cycle, multilayered papillary epithelium develops from simple flat to cuboidal epithelium but reverts back to simple flat to cuboidal epithelium by term. The most important functions of human surface epithelium of ovaries are its role in transport and exchange between peritoneal cavity and ovaries, and its function in repair and rupture during ovulation. Ovarian surface epithelium undergo epithelio-mesenchymal transformation to replace ovarian stroma in ovulatory repair. The previous proposition regarding the origin of epithelial ovarian cancers was that these tumors originated from surface epithelium of the ovaries and the neoplastic and metaplastic changes led to their differentiation into various histological subtypes such as serous tumors, clear cell carcinoma and endometrioid tumors. But apparent consistencies in this theory has led to development of alternate theories such as origin of neoplastic cells from fallopian tubes and endometrium.
Causes
Epithelial ovarian tumors' etiology is not completely understood but there are multiple risk factors that can play a role in its occurrence. The theories of the etiology of ovarian cancer suggest that repeated ovulation injures the ovarian epithelium and eventually leads to ovarian cancer development. The other theories discuss the origin of ovarian cancer that can be cortical inclusion cysts that become neoplastic or metaplastic or dysplastic changes of the fallopian tube. Direct effect of persistent Gonadotrophin release from the pituitary gland on the ovary also believed to play a role in ovarian cancer etiology.
Differentiating Epithelial Ovarian Tumors from Other Diseases
On the basis of age of onset, vaginal discharge, and constitutional symptoms, ovarian cancer must be differentiated from tubo-ovarian abscess, ectopic pregnancy, hydrosalpinx, salpingitis, fallopian tube carcinoma, uterine leiomyoma, choriocarcinoma, leiomyosarcoma, pregnancy, appendiceal abscess, appendiceal neoplasm, diverticular abscess, colorectal cancer, pelvic kidney, advanced bladder cancer, and retroperitoneal sarcoma.