An ovarian cyst is a fluid-filled sac within the ovary; the obvious concern of patients with ovarian masses is the presence of malignancy

Aetiology

• Ovarian masses can be benign, borderline, malignant or metastatic
• Tumours can arise from any of the 3 cell types in the ovary: surface epithelium (most common), germ cell (more common in women <40 years), sex cord

Risk factors for malignancy

• Ovarian cancers are believed to derive from surface epithelial irritation during ovulation
• Therefore, the more ovulations that take place, the increased risk of developing malignancy:
  • Nulliparity
  • Early menarche/late menopause
  • HRT containing oestrogen only
  • Smoking
  • Obesity
• There is also a genetic component to ovarian cancer - BRCA1 and 2, Lynch II syndrome

Pathophysiology

Classification of ovarian cysts (benign)

• No cytological abnormalities, proliferative activity absent or scant
• No stromal invasion

Non-neoplasic

• Functional:
  • Follicular cysts: can form when ovulation doesn't occur, follicle doesn't rupture but grows until it becomes a cyst
    • Thin walled, lined with granulosa cells
    • Rarely >5cm diameter
    • Usually resolve spontaneously over a few months
    • May cause menstrual disturbance
    • Consider as differential in acute abdomen as may bleed or rupture
    • Often asymptomatic/incidental finding
  • Corpus luteal cysts: occur in the luteal phase of the menstrual cycle after the normation of the corpus luteum
• Pathological:
  • Endometrioma (’chocolate cysts’) - the presence of endometrial glands and stroma outside the uterine body
  • Polycystic ovaries
  • Theca lutein cyst - result as a consequence of markedly raised hCG e.g. molar pregnancy, regress upon resolution of the raised hCG

Benign neoplasic

• Epithelial:
  • Serous cystadenoma
  • Mucinous cystadenoma
  • Brenner tumour: tumour of transitional type epithelium, usually benign, borderline and malignant variants are rare
• Benign germ cell tumours: mature cystic teratoma (Dermoid cyst)
  • Usually occur in young women, occur frequently in pregnancy
  • As germ cell in origin they can contain teeth, hair, skin and bone
• Sex-cord stromal tumours:
  • Fibroma: may produce oestrogen causing uterine bleeding
  • Sertoli-Leydig cell tumours: rare sex cord tumours, may produce androgens

Borderline ovarian tumours