Pelvis Mass

Eva Ilse Rubio, MD

DIFFERENTIAL DIAGNOSIS

Common

Ovarian Lesion, Nonneoplastic
- Simple Cyst
- Parovarian Cyst
- Hemorrhagic Cyst
Ovarian Lesion, Neoplastic
- Germ Cell Tumors
- Stromal Cell Tumors
- Epithelial Cell Tumors
Ovarian Torsion
Duplication Cyst, GI Tract

Less Common

Genitourinary Anomalies
- Obstructed Urinary Bladder
- Horseshoe Kidney
- Cloaca
- Hydrometrocolpos/Hematometrocolpos
Lymphoma (Burkitt)
Sacrococcygeal Teratoma
Anterior Sacral Meningocele
Neuroblastoma
Desmoid
Ewing Sarcoma
Rhabdomyosarcoma, Genitourinary

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

Gender and age of patient

Helpful Clues for Common Diagnoses

Ovarian Lesion, Nonneoplastic
- Simple Cyst
  - Anechoic, larger than 3-5 cm
  - If large, may cause torsion; occasionally large enough to extend into abdomen
- Parovarian Cyst
  - Wolffian duct remnant; anechoic
  - Appearance/size will not change with time
- Hemorrhagic Cyst
  - Appearance depends on chronicity
  - May be echogenic/solid, lacy/septated, or mixed with fluid-debris levels
Ovarian Lesion, Neoplastic
- Germ Cell Tumors
  - Various types: Teratoma, dysgerminoma, yolk sac tumor, embryonal cell carcinoma, choriocarcinoma
  - Most common teratoma features are
  - Mixed cystic, solid, calcified elements
  - Fat within lesion well seen on CT
  - Identifying teeth “clenches” diagnosis
  - May be bilateral
  - “Tip of iceberg” sign: Posterior acoustic shadows of teeth/bone/calcifications obscure full extent of mass
- Stromal Cell Tumors
  - Granulosa cell tumor: Often solid; may cause sexual precocity
  - Leydig cell tumors: Cystic, solid, or mixed; often cause virilization
- Epithelial Cell Tumors
  - e.g., cystadenoma, cystadenocarcinoma
  - Predominantly cystic appearance
  - Uncommon in children
Ovarian Torsion
- Marked asymmetry in ovarian volumes
- Appearance varies with chronicity
  - Hypoechoic or heterogeneous
  - Peripheral follicles often seen
- Presence of blood flow may reflect intermittent torsion or multiple vessels serving ovary
- Underlying cyst or mass is common
Duplication Cyst, GI Tract
- Often round or tubular; may be multiple
- Hypoechoic on US, low attenuation on CT
  - On US may see bowel wall layers (echogenic mucosa, serosa, intervening hypoechoic muscularis)

Helpful Clues for Less Common Diagnoses

Genitourinary Anomalies
- Obstructed Urinary Bladder
  - Must search for structural anomalies, i.e., posterior urethral valves, cloaca, spinal cord anomaly, obstructing mass
- Horseshoe Kidney
  - May be partially obstructed or multicystic
  - Increased risk of infections, Wilms tumor, or injury (superficial location)
- Cloaca
  - Large fluid-filled structure(s) often seen
  - Complex anatomic abnormalities associated with anorectal malformations, vaginal/uterine anomalies
  - Search for coexisting upper urinary tract anomalies or obstructive hydronephrosis
- Hydrometrocolpos/Hematometrocolpos
  - Without cloacal anomaly
  - More commonly seen in teenagers but occasionally seen in neonates
  - Causes range from simple imperforate hymen to complex Müllerian duct anomalies
  - Expect to see bulging structures filled with fluid, debris, &/or blood products
Lymphoma (Burkitt)
- Commonly involves abdominal/pelvic organs, especially distal bowel
- Clinically causes obstruction or intussusception
- Suggestive imaging findings
  - US: Hypoechoic, mildly heterogeneous
  - CT: Homogeneous, wall thickening, adenopathy
  - MR: Homogeneous, intermediate/bright signal
Sacrococcygeal Teratoma
- Heterogeneous, mixed cystic/solid mass
- Calcifications common but not universal
- Prognosis depends on prompt diagnosis; higher risk of malignancy after 2 months
  - Type 1 is extrapelvic
  - Type 2 is predominantly extrapelvic, small intrapelvic component
  - Type 3 is predominantly intrapelvic, small extrapelvic component
  - Type 4 is entirely intrapelvic, delayed diagnosis is therefore common
Anterior Sacral Meningocele
- Usually purely cystic in appearance
- Few associated with Currarino triad
- Other considerations: Neurofibromatosis, Marfan syndrome
Neuroblastoma
- Arises from neural crest cells in sympathetic chain ganglia or adrenal medulla
- Poorly marginated, encases vessels
- Typical CT/US/MR findings
  - Heterogeneous soft tissue mass with calcifications, necrosis, hemorrhage
  - Metastases typically to liver, skin (younger ages), and bones (older children)
Desmoid
- Benign tumor with well-marginated or infiltrating margins
- CT and MR imaging characteristics depend upon histologic features, relative amounts of collagen, spindle cells
Ewing Sarcoma
- Pelvic origin not uncommon
- Soft tissues: Large heterogeneous mass is commonly seen
- Bone: May be lytic, sclerotic, or mixed, with periosteal reaction
Rhabdomyosarcoma, Genitourinary
- May arise from any pelvic structure: Bladder, vagina, uterus, or prostate
- Polypoid appearance is typical but not universal
- Hydronephrosis is common finding