Primary Types of Ovarian Malignancy
Ovarian malignancies are classified into three major categories: epithelial ovarian cancers (90%), germ cell tumors (5%), and sex cord-stromal tumors (3-5%), each with distinct subtypes, clinical presentations, and treatment approaches. 1
Epithelial Ovarian Cancers (90% of ovarian malignancies)
High-Grade Serous Carcinoma (70-80%)
- Most common subtype, typically presents at advanced stages (FIGO III-IV)
- Characterized by papillary architecture, solid growth with slit-like spaces
- Often originates from the fallopian tube rather than the ovary itself
- Poor prognosis, but typically responsive to platinum-based chemotherapy 1
Low-Grade Serous Carcinoma (<5%)
- Distinct entity from high-grade serous carcinoma
- Characterized by low-grade cell atypia and low mitotic activity
- Often presents in younger patients with more indolent disease
- Less responsive to conventional chemotherapy 1
Endometrioid Carcinoma (10%)
- Second most common epithelial subtype
- Often diagnosed at early stages (FIGO I-II)
- May be associated with endometriosis
- Positive for CK7, PAX8, CA 125, and estrogen receptors
- Generally has a better prognosis than serous carcinomas 1
Clear Cell Carcinoma (5-10%)
- More common in Japanese women
- Usually diagnosed at early stages
- Considered high-grade tumors
- Typically negative for WT1 and estrogen receptors
- Associated with endometriosis 1
Mucinous Carcinoma (3%)
- Important to distinguish from metastatic gastrointestinal tumors
- Often presents as large, unilateral masses
- Better prognosis when diagnosed at early stages 1
Transitional Cell Carcinoma (rare)
- Most have features and immunophenotype similar to high-grade serous carcinomas
- Express WT1 and p53 1
Germ Cell Tumors (5% of ovarian malignancies)
- Primarily affect young women (median age 16-20 years)
- Most common ovarian tumor in adolescents and young adults
- Excellent prognosis with >85% 5-year survival rate 1
Main subtypes:
- Dysgerminomas: Most chemosensitive germ cell tumor
- Immature teratomas: Graded based on amount of immature neuroepithelial tissue
- Endodermal sinus (yolk sac) tumors: Associated with elevated AFP
- Embryonal tumors: Aggressive behavior 1, 2
Sex Cord-Stromal Tumors (3-5% of ovarian malignancies)
- Often produce hormones causing clinical manifestations
- Generally diagnosed at earlier stages than epithelial cancers
- Lower incidence of lymph node metastases 1
Main subtypes:
- Granulosa cell tumors: Most common SCST, often produces inhibin
- Adult type: Average age 50 years
- Juvenile type: 90% in pre-pubertal girls
- Sertoli-Leydig cell tumors: Typically in women under 40 years
- Thecomas: Primarily in peri/postmenopausal women 1, 3
Other Rare Ovarian Malignancies
- Carcinosarcomas (Malignant Mixed Müllerian Tumors): Aggressive behavior
- Small cell carcinoma: Very rare (<1%), affects young women and children
- Borderline tumors: Intermediate between benign and malignant, excellent prognosis 1, 4
Clinical Implications
- Histologic classification is critical for treatment planning and prognosis
- Different subtypes require different surgical and chemotherapeutic approaches
- Fertility preservation is often possible with germ cell and sex cord-stromal tumors
- Tumor markers (CA-125, inhibin, AFP, β-hCG) vary by tumor type and aid in diagnosis and monitoring 1, 2, 5
Understanding the specific histologic subtype is essential as each type represents a distinct disease with unique molecular pathways, treatment responses, and outcomes. Recent evidence suggests many "ovarian" cancers actually originate in the fallopian tube or endometrium and involve the ovary secondarily 1, 6.