Low-grade epithelial ovarian cancer: what a radiologist should know

Abstract

Ovarian cancer is responsible for the death of over 100,000 females annually. 1 Much of the published medical literature regards the various histologically distinct subtypes of epithelial ovarian neoplasms as one group, and almost all patients with advanced stage disease are treated with the standard therapy of debulking surgery followed by platinum-based adjuvant chemotherapy. However, recent studies have questioned this "one-size-fits-all" concept and advocated for another theory that ovarian cancer comprise of a spectrum of diverse tumors, each with characteristic histological and molecular features that determine its behavior and prognosis. 1-3 In 2004, Malpica and colleagues at the MD Anderson Cancer Center (MDACC) proposed a novel binary grading system for serous ovarian carcinoma, the most common histological subtype of ovarian cancer. This MDACC binary grading system was mainly based on nuclear atypia, in addition to the mitotic index. They found substantial correlation between tumor grade and survival rate. Bodurka et al 2 assessed the two-tier grading system in 290 patients with Stage III serous ovarian carcinoma and found that this grading system had minimal interobserver variability as it was reproducible among pathologists. Their study supported the theory that grade II and III tumors were better grouped together as they have a similar clinical outcome and prognosis. 2 Low-grade serous ovarian carcinomas are a distinct group with a longer progression-free survival (PFS) and overall survival (OS) compared to highgrade serous ovarian carcinomas (45 vs 19.8 and 126.2 vs 53.8, respectively). 2 Since the binary grading system helps to stratify the clinical outcomes and treatment strategies of ovarian neoplasms, the two-tier MDACC grading system is currently used for grading of serous ovarian carcinoma rather than the traditional three-tier grading system. 2,4,5 This article reviews the recent literature addressing the staging and follow-up of low-grade epithelial ovarian cancer with the main emphasis on serous ovarian cancer. clASSificAtion Embryologically, ovarian tumors are grouped into three major categories based on their origin: epithelial-stromal tumors, sex cord-stromal tumors, and germ cell tumors. Malignant epithelial tumors account for 90-98% of ovarian cancer and can be subdivided into five main groups: high-grade serous ovarian carcinoma (HGSOC) (70%), low-grade serous ovarian carcinoma (LGSOC) (<5%), clear cell carcinoma (10%), endometrioid carcinoma (EC) (10%) and mucinous carcinoma (1.5-3%). 6,7 Other less common subtypes of malignant epithelial neoplasms that are included in the new 2014 WHO Classification of Ovarian Cancer 8 include malignant Brenner tumors and seromucinous carcinoma. 9

Recurrence characteristics and clinicopathological results of borderline ovarian tumors

“…Prognosis is much better than that of ovarian cancer of the same clinical stage [ 1 , 4 ]. BOTs account for 10%–15% of ovarian epithelial tumors, and their staging is based on the FIGO staging system of ovarian cancer [ 2 ]. At the time of diagnosis, 75% of patients with BOTs are at an early stage.…”

Ovarian Cancer: Molecular Classification and Targeted Therapy

“…β-catenin signaling is a conserved pathway involved in development implicated in other epithelial cancers but its oncogenic role is less understood [75]. Other less frequent mutations are KRAS/ BRAF (20%), which are regulators of MAPK pathways, PIK3CA (12%), and TP53 (25%) [76]. PTEN mutations with frequent loss of heterozygosity (45-75%) is also reported [52].…”

Low-grade serous epithelial ovarian cancer: a comprehensive review and update for radiologists

“…Ovarian tumours are divided into epithelial neoplasms, mesenchymal neoplasms, sex cord-stromal tumours, and germ cell tumours [ 1 , 2 ].…”

“…LGSC and HGSC have different morphology, pathogenesis, associated molecular events, response to chemotherapy, and prognosis [ 1 , 4 – 6 ].…”

“…LGSC is an invasive serous tumour presenting low-grade malignant features that is diagnosed at a young age (median age between 43 and 47), has an indolent clinical course, and is relatively chemoresistant [ 1 , 4 ]. LGSC is also associated with longer progression-free survival and overall survival than HGSC [ 1 ].…”