Definition/General
Introduction:
Mature teratoma is the most common ovarian germ cell tumor
Also known as dermoid cyst or benign cystic teratoma
Accounts for 95% of ovarian teratomas
Contains mature tissues from all three germ layers.
Origin:
Originates from totipotent germ cells with complete differentiation
Shows mature tissues from ectoderm, mesoderm, and endoderm
Most commonly contains ectodermal derivatives (skin, hair, teeth)
No immature elements present.
Classification:
Benign mature teratoma (most common)
Mature teratoma with malignant transformation (1-2%)
Monodermal teratomas (struma ovarii, carcinoid)
Solid mature teratoma (rare)
WHO classification: Germ cell tumor, mature teratoma.
Epidemiology:
Peak incidence in reproductive age group (20-40 years)
Most common ovarian tumor in young women
Bilateral in 10-15% cases
Accounts for 20% of all ovarian tumors
Indian population shows similar prevalence.
Clinical Features
Presentation:
Asymptomatic pelvic mass (often incidental finding)
Abdominal/pelvic pain (intermittent)
May present with acute abdominal pain (torsion)
Abdominal distension (large tumors)
No hormonal effects typically.
Symptoms:
Pelvic/abdominal pain (40-60%)
Abdominal fullness (30-40%)
Urinary frequency (pressure symptoms)
Acute severe pain (ovarian torsion 10-15%)
Asymptomatic (30-50%)
Menstrual irregularities (rare).
Risk Factors:
Reproductive age (most common risk factor)
Family history (rare)
Previous ovarian cysts
No established environmental factors
Genetic predisposition unclear
Hormonal factors (unclear association).
Screening:
Pelvic ultrasound (characteristic echogenic focus)
CT scan (fat density, calcifications)
MRI (fat signal, chemical shift)
Serum tumor markers usually normal
CA-125 (usually normal)
AFP (normal).
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Gross Description
Appearance:
Smooth, unilocular cystic mass with intact capsule
Contains sebaceous material, hair
Rokitansky nodule (solid protuberance)
Size ranges from 2-25 cm (average 6-8 cm)
Teeth, bone, cartilage may be present.
Characteristics:
Unilateral in 85-90% cases
Smooth capsule with gray-white surface
Contains thick, greasy sebaceous material
Hair of various colors
Rokitansky nodule contains solid tissues
Calcified structures (teeth, bone).
Size Location:
Variable size (1-30 cm diameter)
Average size 5-10 cm
Usually smaller than immature teratomas
No specific ovarian location preference
Slow growth pattern
Surface usually smooth and intact.
Multifocality:
Usually unifocal within affected ovary
Bilateral in 10-15% (higher than most ovarian tumors)
Multiple small cysts may coexist
Rarely multifocal within same ovary
Peritoneal spillage may cause chemical peritonitis.
Microscopic Description
Histological Features:
Mature tissues from all three germ layers
Keratinizing squamous epithelium (ectoderm)
Hair follicles and sebaceous glands
Smooth muscle, cartilage, bone (mesoderm)
Respiratory, gastrointestinal epithelium (endoderm).
Cellular Characteristics:
Well-differentiated mature tissues
Keratinized squamous epithelium with normal maturation
Hair shafts and follicular structures
Sebaceous glands with typical morphology
Smooth muscle bundles
Mature cartilage and bone.
Architectural Patterns:
Cystic spaces lined by keratinizing epithelium
Solid areas with various tissue types
Hair follicles with sebaceous glands
Respiratory epithelium with cilia
Intestinal-type epithelium
Neural tissue (brain, glial).
Grading Criteria:
No grading system for mature teratoma
All tissues are mature and well-differentiated
No immature elements present
Malignant transformation occurs in 1-2% (usually squamous cell carcinoma)
Age >40 years higher risk for malignant transformation.
Immunohistochemistry
Positive Markers:
SALL4 (germ cell origin, focal)
Cytokeratin (epithelial components)
Vimentin (mesenchymal components)
Smooth muscle actin (smooth muscle areas)
S-100 (neural components)
Tissue-specific markers based on components.
Negative Markers:
AFP (negative)
Beta-hCG (negative)
OCT4 (negative)
CD117 (negative)
PLAP (negative)
Inhibin (negative)
Calretinin (negative)
Chromogranin (negative unless neuroendocrine tissue).
Diagnostic Utility:
Usually not required for diagnosis
Tissue-specific markers confirm differentiation
SALL4 may be focally positive
Negative germ cell markers (AFP, OCT4, PLAP)
Cytokeratin patterns vary by tissue type.
Molecular Subtypes:
Parthenogenetic origin (development from single gamete)
Chromosomal abnormalities rare
Stable karyotype typically
Low mutation burden
Epigenetic alterations in development
Different from somatic tumors.
Molecular/Genetic
Genetic Mutations:
Parthenogenetic development from unreduced ovum
Homozygous at all loci (genetic fingerprinting)
Low mutation rate
Chromosomal stability
Rare oncogene mutations
Malignant transformation associated with TP53, KRAS mutations.
Molecular Markers:
Tissue-specific gene expression
Developmental gene expression patterns
Low proliferative activity
Stable DNA content
Normal p53 expression
Ki-67 low in mature areas.
Prognostic Significance:
Excellent prognosis for pure mature teratoma
Age >40 years increased malignant transformation risk
Size >10 cm may have higher complications
Bilateral disease does not affect prognosis
Malignant transformation worsens prognosis significantly.
Therapeutic Targets:
Surgical excision curative
Cystectomy (organ-sparing)
Oophorectomy (if necessary)
Laparoscopic approach preferred
No chemotherapy required
Fertility preservation important consideration.
Differential Diagnosis
Similar Entities:
Immature teratoma (contains immature neural tissue)
Endometrioma (chocolate cyst, different contents)
Dermoid plug vs Rokitansky nodule
Sebaceous cyst (simpler, different location)
Malignant transformation (squamous cell carcinoma).
Distinguishing Features:
Mature teratoma: Hair, teeth, sebaceous material
All mature tissues
Immature teratoma: Contains immature neural tissue
Younger patients
Endometrioma: Chocolate-colored contents
Endometrial tissue
Sebaceous cyst: Simple cyst
No hair or teeth
Malignant: Cytologic atypia
Invasive growth.
Diagnostic Challenges:
Distinguishing mature from immature elements
Malignant transformation recognition
Sampling adequacy important
Bilateral disease assessment
Spillage complications
Torsion complications.
Rare Variants:
Solid mature teratoma (predominantly solid)
Fetiform teratoma (fetus-like)
Mature teratoma with malignant transformation
Monodermal teratomas (struma ovarii, carcinoid)
Proliferative nodules
Secondary tumors arising in teratoma.
Sample Pathology Report
Template Format
Sample Pathology Report
Complete Report: This is an example of how the final pathology report should be structured for this condition.
Specimen Information
Ovarian cyst, [side], measuring [X x Y x Z] cm
Diagnosis
Mature Teratoma (Dermoid Cyst)
Classification
WHO Classification: Germ Cell Tumor, Mature Teratoma
Histological Features
Shows mature tissues from all three germ layers without immature elements
Tissue Components
Ectoderm: [list], Mesoderm: [list], Endoderm: [list]
Malignant Transformation
[Present/Absent], type: [if present]
Special Studies
IHC: [if performed] - tissue-specific markers positive
Imaging correlation: [consistent with dermoid cyst]
Tumor markers: [normal/not indicated]
Prognostic Factors
Age: [X] years, Size: [X] cm, Bilaterality: [yes/no], Malignant transformation: [yes/no]
Final Diagnosis
Ovarian Mature Teratoma (Dermoid Cyst), [Side]