Gynaecological Abdominal / Pelvic Mass

Based on Berek & Novak's Gynecology (Berek & Novak's Gynecology)

Classification & Differential Diagnosis

The single most important framework for gynaecological pelvic masses is the adnexal mass algorithm:

Causes of Pelvic Mass by Category (Reproductive-Age Women)

Urinary / Non-Gynae Mimics

Full urinary bladder
Urachal cyst
Stool in sigmoid colon
Peritoneal cyst
Matted bowel/omentum

Uterine Masses

Condition	Notes
Sharply anteflexed or retroflexed uterus	Feels like a mass on bimanual
Leiomyomas (Fibroids)	Most common benign uterine tumor; often asymptomatic
Intraligamentous leiomyomas	Can mimic adnexal mass
Intrauterine pregnancy	Always exclude first
Tubal (ectopic) pregnancy	Lateral adnexal mass, tender
Abdominal pregnancy	Rare
Uterine sarcoma	Rare malignant cause

Uterine leiomyomas are by far the most common benign uterine tumors; they are more prevalent in African American women.

Ovarian / Adnexal Masses

Functional (non-neoplastic):

Follicular cyst - most common; usually resolves spontaneously
Corpus luteal cyst - can bleed causing acute pain
Pregnancy luteoma

Neoplastic - Benign:

Type	Examples
Germ cell (benign)	Benign cystic teratoma (dermoid) - most common in women <20 yrs; accounts for >50% of ovarian neoplasms in this group
Epithelial	Serous cystadenoma, Mucinous cystadenoma
Sex-cord stromal	Fibroma, Thecoma, Granulosa cell, Sertoli-Leydig cell
Other	Endometrioma ("chocolate cyst"), Paraovarian/paratubal cyst, Polycystic ovaries

Neoplastic - Borderline (Low Malignancy Potential):

Serous or mucinous borderline tumours

Neoplastic - Malignant:

Type	Examples
Epithelial (most common)	Serous/mucinous cystadenocarcinoma, Endometrioid, Clear cell, Brenner
Germ cell (malignant)	Dysgerminoma, Yolk sac tumour, Immature teratoma
Metastatic	From endometrium, appendix, breast, colon, carcinoid, pancreas, stomach (Krukenberg)

Inflammatory Masses

Tubo-ovarian abscess (TOA) / complex
Diverticular abscess
Appendiceal abscess

Less Common But Must Exclude

Pelvic kidney
Carcinoma of colon, rectum, appendix
Carcinoma of the fallopian tube
Retroperitoneal tumours (anterior sacral meningocele)

Causes by Age Group (Approximate Frequency)

Age Group	Most Likely Causes
Infancy	Functional cyst, Germ cell tumour
Prepubertal	Functional cyst, Germ cell tumour
Adolescent	Functional cyst, Pregnancy, Benign cystic teratoma/germ cell, Obstructive uterovaginal anomalies, Epithelial tumour
Reproductive	Functional cyst, Pregnancy, Uterine fibroids, Epithelial ovarian tumour, Endometrioma
Perimenopausal	Fibroids, Epithelial ovarian tumour, Functional cyst
Postmenopausal	Ovarian tumour (malignant or benign), Functional cyst, Bowel malignancy/inflammatory, Metastases

Key point on malignancy risk: In women undergoing laparotomy for pelvic mass, malignancy was found in only 10% of those under 30, and most had low-malignancy-potential tumours. Mature cystic teratomas (dermoids) account for one-third of masses in women <30; endometriomas account for ~one-quarter in those aged 31-49.

Features Suggesting Benign vs. Malignant

Feature	Likely Benign	Likely Malignant
Laterality	Unilateral	Bilateral
Consistency	Cystic	Solid or mixed
Mobility	Mobile	Fixed
Surface	Smooth	Irregular
Ascites	Absent	Present
Cul-de-sac nodules	Absent	Present
Growth rate	Slow	Rapid

Investigations

Pregnancy test - mandatory in all women of reproductive age regardless of stated sexual activity
Transvaginal ultrasound (TVS) - primary diagnostic tool; characterises cystic vs. solid, uni- vs. multilocular, Doppler flow
Transabdominal USS - useful in adolescents who may not tolerate TVS; also for large masses
CT / MRI - for complex masses, staging malignancy, retroperitoneal extension
Tumour markers:
- CA-125 - epithelial ovarian cancer (also raised in endometriosis, fibroids, PID)
- AFP (alpha-fetoprotein) + beta-hCG - germ cell tumours
- CEA - mucinous tumours / bowel primary
- Inhibin - granulosa cell tumours
CBC - leucocytosis suggests inflammatory mass (TOA)
Doppler flow studies - helpful in ovarian torsion

Key Clinical Points

Uni- and multilocular simple cysts often resolve with observation; a solid component mandates surgical assessment due to high risk of germ cell tumour (especially in prepubertal girls)
Ovarian torsion - acute onset severe pain + nausea/vomiting; Doppler flow may not reliably predict torsion; management is detorsion (not oophorectomy), even with absent flow, as ovarian recovery is likely
Endometriosis in adolescents may have atypical appearance (non-pigmented, vesicular lesions); up to 70% of adolescents not responding to conventional analgesia have endometriosis at laparoscopy
Referral to a gynecologic oncologist is recommended when a pelvic mass is suspicious on USS
In postmenopausal women, any pelvic mass warrants prompt evaluation for malignancy

Berek & Novak's Gynecology, pp. 391-392, 415-419, 448-450

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