Benign Ovarian Cysts & Tumours

Benign ovarian masses range from harmless functional cysts that resolve on their own to true neoplasms (epithelial, germ cell, sex-cord) that may need surgery. For NEET PG, the high-yield anchors are: the commonest benign tumour (serous cystadenoma), the commonest tumour in young women (dermoid/mature cystic teratoma), characteristic ultrasound signatures, the rule of torsion management, and the malignancy-risk scoring used to triage.

Classification

Ovarian enlargements are first split into non-neoplastic (functional/inflammatory) and neoplastic (true tumours). Neoplastic tumours follow the WHO cell-of-origin scheme.

Category	Examples	Key point
Functional (non-neoplastic)	Follicular cyst, corpus luteum cyst, theca-lutein cyst	Resolve spontaneously; never become malignant
Inflammatory	Tubo-ovarian abscess, endometrioma ("chocolate cyst")	Endometrioma is technically not neoplastic
Epithelial neoplasm	Serous & mucinous cystadenoma, Brenner tumour	Commonest group of true neoplasms
Germ cell neoplasm	Mature cystic teratoma (dermoid)	Commonest tumour in women < 30 yr
Sex-cord stromal	Fibroma, thecoma	Fibroma → Meigs syndrome

High-yield: The commonest benign ovarian tumour overall is the serous cystadenoma. The commonest benign tumour in young women (and the commonest ovarian neoplasm in pregnancy) is the mature cystic teratoma (dermoid cyst).

Functional cysts

These arise from normal follicular dynamics and are by far the most common ovarian "cysts."

Follicular cyst

• Failure of a mature Graafian follicle to rupture (no ovulation) → continued fluid accumulation.
• Most common functional cyst; usually < 8 cm, unilocular, thin-walled, anechoic on USG.
• Asymptomatic; may cause menstrual irregularity. Resolves in 4–8 weeks (1–2 cycles).

Corpus luteum cyst

• Persistence/haemorrhage into the corpus luteum after ovulation.
• Associated with delayed menses then pain — mimics ectopic pregnancy. A ruptured haemorrhagic corpus luteum is a classic cause of acute haemoperitoneum (esp. on the right, in patients on anticoagulants).
• Halban syndrome = persistent corpus luteum cyst → amenorrhoea + pain + adnexal mass simulating ectopic.

Theca-lutein cyst

• Caused by high β-hCG stimulation → bilateral, multilocular, often large cysts.
• Seen with molar pregnancy, choriocarcinoma, multiple gestation, ovulation induction (OHSS).
• Regress once hCG falls.

High-yield: Bilateral large multicystic ovaries + very high β-hCG = theca-lutein cysts, the hallmark ovarian finding in hydatidiform mole.

Epithelial benign tumours

Serous cystadenoma

• Commonest benign ovarian neoplasm. Lined by ciliated tubal-type epithelium.
• Often bilateral (~10–20%), unilocular, thin-walled, contains clear/straw-coloured serous fluid.
• Psammoma bodies (concentric calcified laminations) may be seen; far more numerous in the serous malignant counterpart.

Mucinous cystadenoma

• Second commonest; lined by tall mucin-secreting (endocervical/intestinal-type) columnar epithelium.
• Usually unilateral, multiloculated, and the LARGEST ovarian tumour — can fill the entire abdomen.
• Rupture/spillage can cause pseudomyxoma peritonei (gelatinous peritoneal deposits) — though this is now considered more often appendiceal in origin.

Brenner tumour

• Solid, usually small and incidental. Composed of transitional (urothelial-like) epithelial nests with "coffee-bean" grooved nuclei in a fibrous stroma. Mostly benign.

Feature	Serous cystadenoma	Mucinous cystadenoma
Frequency	Most common benign neoplasm	Second most common
Laterality	Often bilateral	Usually unilateral
Loculation	Unilocular	Multilocular
Size	Moderate	Largest ovarian tumour
Lining	Ciliated (tubal-type)	Mucin-secreting columnar
Classic finding	Psammoma bodies	Pseudomyxoma peritonei (on rupture)

Mature cystic teratoma (Dermoid cyst)

The single most exam-relevant benign tumour.

• A germ cell tumour containing well-differentiated tissue from all three germ layers (ectoderm predominant → hair, sebum, teeth, skin).
• Commonest ovarian tumour in reproductive-age/young women and commonest in pregnancy; bilateral in ~10–15%.
• Most common ovarian tumour to undergo torsion (because of high fat content → buoyant) and the most common to cause torsion in pregnancy.
• Rokitansky's protuberance (dermoid plug/Rokitansky tubercle): a solid mound projecting into the cyst lumen where hair, teeth and bone arise — the site from which malignant transformation (squamous cell carcinoma, ~1–2%) may occur.

USG/imaging signatures (very testable):

• Rokitansky nodule with acoustic shadowing.
• "Tip of the iceberg" sign — dense echoes from hair/fat cause shadowing that obscures deeper structures.
• "Dermoid mesh / dot-dash" pattern — echogenic lines and dots from hair strands.
• Floating fat–fluid level; teeth visible as calcific densities on X-ray/CT.

High-yield: Rokitansky's tubercle is the origin of malignant change in a dermoid; the malignancy is usually squamous cell carcinoma. "Tip-of-the-iceberg" sign on USG = dermoid.

Related germ cell entities:

• Struma ovarii = teratoma composed predominantly of thyroid tissue → can cause hyperthyroidism.
• Carcinoid within teratoma → carcinoid syndrome without liver mets (drains systemically).

Sex-cord stromal & endometriotic lesions

• Fibroma: Commonest benign solid ovarian tumour; estrogen-inactive. Associated with Meigs syndrome = ovarian fibroma + ascites + right-sided hydrothorax, all of which resolve after tumour removal. (Pseudo-Meigs = same triad with other tumours.)
• Endometrioma ("chocolate cyst"): Ectopic endometrium in the ovary; old altered blood gives thick brown content. USG shows homogeneous low-level "ground-glass" internal echoes. CA-125 mildly raised; associated infertility and dysmenorrhoea.

Pathophysiology of complications

Benign masses become emergencies through mechanical events:

Torsion mechanism: Mobile, moderately heavy mass (dermoid most common) → ovary + tube twist on the infundibulopelvic & utero-ovarian ligaments → venous/lymphatic outflow obstructed first → congestion & oedema → arterial compromise → ischaemic necrosis.

Stepwise clinical flow of suspected torsion: Sudden severe unilateral pelvic pain + nausea/vomiting → palpable tender adnexal mass → USG with Doppler showing enlarged oedematous ovary, peripheralised follicles ("string of pearls"), ± absent/reduced flow → emergency laparoscopy → detorsion + ovarian conservation (cystectomy) → oophorectomy only if frankly necrotic.

High-yield: Doppler flow may still be present in early torsion (dual ovarian + uterine blood supply), so normal flow does NOT exclude torsion — diagnosis is clinical/operative. Treat with detorsion and conservation, not reflex oophorectomy, even if the ovary looks dusky.

Other complications: rupture (chemical peritonitis with dermoid; haemoperitoneum with corpus luteum), haemorrhage, infection, pressure effects (urinary frequency, constipation), and malignant change (dermoid → SCC; serous/mucinous → borderline/carcinoma).

Clinical features

• Often asymptomatic, found incidentally on USG.
• Dull pelvic pain/heaviness, dyspareunia, abdominal distension (large mucinous), pressure symptoms.
• Acute presentation = torsion, rupture, or haemorrhage.
• Menstrual disturbance with functional cysts; hormone effects with functional sex-cord tumours.

Diagnosis & investigation of choice

Transvaginal ultrasound (TVS) is the investigation of choice for characterising an adnexal mass. Reassuring (benign) sonographic features:

• Unilocular, anechoic, thin smooth wall (< 3 mm).
• No solid components, no thick septa, no internal vascularity, no ascites.

IOTA simple rules classify masses as benign (B-features) vs malignant (M-features); presence of any M-feature (solid component, irregular multilocular solid, ascites, strong colour Doppler flow, papillary projections ≥ 4) suggests malignancy.

Tumour markers (use age-appropriately):

Marker	Raised in
CA-125	Epithelial ovarian cancer; also endometrioma, PID, fibroids (low specificity premenopausally)
β-hCG	Choriocarcinoma, dysgerminoma component, theca-lutein context
AFP	Yolk sac (endodermal sinus) tumour
LDH	Dysgerminoma
Inhibin	Granulosa cell tumour

Risk stratification — RMI (Risk of Malignancy Index): RMI = U × M × CA-125, where U = ultrasound score (multilocular, solid areas, bilateral, ascites, intra-abdominal mets → 0/1/3), M = menopausal status (premenopausal = 1, postmenopausal = 3), and CA-125 in U/mL. RMI > 200 (often > 250) → refer to gynae-oncology.

High-yield: AFP ↑ → yolk sac tumour; LDH ↑ → dysgerminoma; inhibin ↑ → granulosa cell tumour; β-hCG ↑ → choriocarcinoma/germ cell. CA-125 is non-specific in premenopausal women.

Management / treatment of choice

Management hinges on age, symptoms, size, sonographic features and menopausal status.

Functional cysts → expectant management. Simple cyst < 5 cm in a premenopausal woman: reassure, repeat USG after 6–8 weeks (one cycle). Most resolve. Combined oral contraceptives do not hasten resolution of existing cysts but prevent new functional cysts.

Stepwise approach to an asymptomatic simple cyst:

1. Premenopausal, < 5 cm, simple → observe, repeat scan in 6–12 weeks.
2. 5–7 cm simple → annual surveillance; consider cystectomy if growing/symptomatic.
3. Postmenopausal, simple, < 5 cm, normal CA-125 → conservative surveillance acceptable.
4. Any size with M-features / high RMI / persistent / symptomatic / suspicion → surgery.

Surgery:

• Ovarian cystectomy (preserve ovary) is preferred in young women and for dermoids/benign neoplasms — done laparoscopically whenever feasible, with care to avoid spillage (dermoid content → chemical peritonitis; mucinous → pseudomyxoma).
• Oophorectomy/salpingo-oophorectomy for postmenopausal women, large/suspicious masses, or non-viable torsed ovary.
• Torsion → emergency laparoscopic detorsion with conservation; cystectomy of the offending cyst at the same or interval sitting.

High-yield: Drug of choice to prevent recurrent functional cysts = combined oral contraceptive pills (suppress ovulation). They do not shrink an existing cyst faster than observation.

Key differentials

• Functional vs neoplastic cyst — functional resolves on repeat scan; neoplastic persists/grows.
• Endometrioma vs haemorrhagic cyst — endometrioma shows persistent ground-glass echoes; haemorrhagic corpus luteum changes/resolves over a cycle.
• Dermoid vs haemorrhagic cyst — dermoid has fat, calcification, Rokitansky nodule.
• Tubo-ovarian abscess — fever, raised inflammatory markers, PID history.
• Ectopic pregnancy — positive β-hCG, empty uterus; corpus luteum cyst and Halban syndrome mimic it.
• Hydrosalpinx / paraovarian cyst — separate from ovary.
• Pedunculated fibroid — Doppler shows pedicle to uterus.
• Borderline/malignant tumour — solid components, septa, ascites, raised markers, high RMI.

Eponyms & named facts (memory bank)

• Rokitansky's tubercle/protuberance — dermoid plug; site of malignant change.
• Meigs syndrome — fibroma + ascites + right hydrothorax.
• Halban syndrome — persistent corpus luteum cyst mimicking ectopic.
• Psammoma bodies — serous tumours.
• Coffee-bean nuclei — Brenner tumour.
• Call–Exner bodies — granulosa cell tumour (malignant, contrast).
• Pseudomyxoma peritonei — ruptured mucinous tumour/appendiceal origin.

Mnemonics:

• Functional cyst causes of theca-lutein: "MOM" = Mole, Ovulation induction/OHSS, Multiple gestation (all high hCG).
• Germ cell markers: "LAD" = LDH–dysgerminoma, AFP–yolk sac, Dβ-hCG context–choriocarcinoma.
• Dermoid trio of signs: "Tip, Dot, Mesh" = tip-of-iceberg, dot-dash, dermoid mesh.

Recently asked / exam angle

• "Commonest benign ovarian tumour?" → Serous cystadenoma. ("Commonest in young women / pregnancy?" → dermoid.)
• "Rokitansky's tubercle is seen in?" → Mature cystic teratoma (dermoid).
• "Largest ovarian tumour?" → Mucinous cystadenoma.
• "Most common ovarian tumour to undergo torsion?" → Dermoid.
• "Tip-of-the-iceberg sign on USG?" → Dermoid cyst.
• "Bilateral theca-lutein cysts seen with?" → Hydatidiform mole / high hCG.
• "Investigation of choice for adnexal mass?" → Transvaginal ultrasound.
• "Triad of Meigs syndrome?" → Fibroma + ascites + right pleural effusion.
• "Marker raised in yolk sac tumour?" → AFP.
• "RMI components?" → USG score × menopausal status × CA-125.
• "Management of ovarian torsion in a young woman?" → Laparoscopic detorsion with ovarian conservation.
• Image-based MCQs: dermoid showing hair/teeth, ground-glass endometrioma, multiloculated mucinous mass.

Rapid revision

1. Serous cystadenoma = commonest benign ovarian neoplasm; often bilateral; psammoma bodies.
2. Mucinous cystadenoma = unilateral, multilocular, LARGEST; rupture → pseudomyxoma peritonei.
3. Dermoid (mature cystic teratoma) = commonest tumour in young women & in pregnancy; all 3 germ layers.
4. Rokitansky's tubercle = dermoid plug; site of malignant change → squamous cell carcinoma.
5. USG dermoid signs = tip-of-iceberg, dermoid mesh, dot-dash, fat-fluid level.
6. Theca-lutein cysts = bilateral, hCG-driven (mole, OHSS, multiple gestation).
7. Halban syndrome = persistent corpus luteum cyst mimicking ectopic pregnancy.
8. Meigs syndrome = fibroma + ascites + right hydrothorax; resolves after excision.
9. TVS is the investigation of choice; benign = unilocular, anechoic, thin wall, no solid/Doppler.
10. Markers: AFP–yolk sac, LDH–dysgerminoma, inhibin–granulosa, β-hCG–choriocarcinoma; CA-125 non-specific premenopausally.
11. RMI = U × M × CA-125; > 200–250 → refer to gynae-oncology.
12. Torsion = detorsion + ovarian conservation; normal Doppler does NOT rule it out; dermoid is the commonest cause.