Definition/General
Introduction:
Struma ovarii is a monodermal teratoma composed predominantly of thyroid tissue
Accounts for 2-5% of mature teratomas
Contains thyroid follicles as the major component
May cause hyperthyroidism in 5-10% cases.
Origin:
Originates from germ cells with specific differentiation toward thyroid tissue
Shows predominantly thyroidal differentiation
Contains thyroid follicles with colloid
May have normal thyroid function or hyperthyroidism.
Classification:
Pure struma ovarii (>50% thyroid tissue)
Struma ovarii with other teratomatous elements
Malignant struma ovarii (rare, <5%)
Functioning struma (causes hyperthyroidism)
Non-functioning struma (most common).
Epidemiology:
Peak incidence in 4th-5th decades
Represents 2-5% of mature teratomas
Unilateral in >95% cases
Hyperthyroidism occurs in 5-10%
More common in iodine-deficient areas.
Clinical Features
Presentation:
Asymptomatic pelvic mass (most common)
Hyperthyroid symptoms (5-10% cases) with palpitations, weight loss
Abdominal/pelvic pain
Abdominal distension
Thyrotoxicosis may be present.
Symptoms:
Pelvic mass (70-80%)
Hyperthyroid symptoms (palpitations, tremor, weight loss)
Abdominal pain (40-50%)
Heat intolerance
Menstrual irregularities
Anxiety and nervousness
Asymptomatic (30-40%).
Risk Factors:
Reproductive age
Iodine deficiency
Family history of thyroid disease
Previous teratomas
Genetic factors unclear
Geographic variations (endemic goiter areas).
Screening:
Thyroid function tests (TSH, T3, T4)
Thyroglobulin levels (elevated)
Pelvic ultrasound
Thyroid scan (may show ovarian uptake)
CA-125 (usually normal)
MRI for characterization.
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Gross Description
Appearance:
Solid, multilocular cystic mass
Brown to green gelatinous contents (colloid-like)
Size ranges from 5-20 cm
Smooth capsule
Resembles thyroid tissue on cut surface.
Characteristics:
Unilateral in >95% cases
Encapsulated appearance
Cut surface shows solid areas with cystic spaces
Brown-green gelatinous material
Honeycomb appearance
May have calcifications.
Size Location:
Variable size (2-25 cm)
Average size 8-12 cm
No specific ovarian location preference
Usually larger than normal teratomas
Slow growth pattern.
Multifocality:
Usually unifocal
Bilateral involvement rare (<5%)
May coexist with other teratomatous elements
Pure thyroid tissue in some cases.
Microscopic Description
Histological Features:
Thyroid follicles of varying sizes filled with colloid
Follicular epithelium resembling normal thyroid
Colloid material similar to thyroid
May have papillary architecture
C-cells may be present.
Cellular Characteristics:
Cuboidal to columnar epithelium lining follicles
Bland nuclear features in benign cases
Eosinophilic colloid filling follicles
Basement membrane intact
Minimal mitotic activity.
Architectural Patterns:
Follicular pattern (most common)
Microfollicular pattern
Macrofollicular pattern
Solid pattern (rare)
Papillary pattern (if malignant transformation).
Grading Criteria:
Benign struma ovarii (>95%)
Malignant struma ovarii (<5%) shows features of thyroid carcinoma
Papillary carcinoma most common malignant type
Follicular carcinoma rare.
Immunohistochemistry
Positive Markers:
Thyroglobulin (95-100%)
TTF-1 (90-95%)
PAX8 (85-90%)
Thyroid peroxidase (80-85%)
Cytokeratin
Calcitonin (C-cells if present).
Negative Markers:
AFP (negative)
Beta-hCG (negative)
Inhibin (negative)
Calretinin (negative)
WT1 (negative)
Chromogranin (negative except C-cells).
Diagnostic Utility:
Thyroglobulin positivity diagnostic
TTF-1 confirms thyroidal origin
PAX8 supports thyroid differentiation
Distinguish from other ovarian tumors
Negative germ cell markers.
Molecular Subtypes:
Similar to thyroid tumors
RAS mutations (follicular pattern)
BRAF mutations (papillary pattern)
RET/PTC rearrangements (papillary)
PAX8/PPARγ (follicular).
Molecular/Genetic
Genetic Mutations:
RAS mutations (NRAS, HRAS, KRAS)
BRAF V600E (papillary carcinoma)
RET/PTC rearrangements
PAX8/PPARγ fusion (follicular carcinoma)
TP53 mutations (anaplastic).
Molecular Markers:
Thyroglobulin expression
TTF-1 expression
PAX8 expression
Thyroid-specific gene expression
Similar to normal thyroid.
Prognostic Significance:
Benign behavior in most cases
Malignant transformation rare (<5%)
Hyperthyroidism resolves after removal
Excellent prognosis overall.
Therapeutic Targets:
Surgical removal curative
Antithyroid medications (preoperatively if hyperthyroid)
Radioiodine therapy (malignant cases)
Thyroid hormone suppression.
Differential Diagnosis
Similar Entities:
Primary thyroid carcinoma metastases
Clear cell carcinoma
Mucinous tumors
Other monodermal teratomas
Thyroid tissue in normal teratoma.
Distinguishing Features:
Struma ovarii: Predominantly thyroid tissue
Ovarian location
Thyroglobulin positive
Metastatic thyroid: Known primary
Bilateral often
Clear cell: Different morphology
Negative thyroid markers.
Diagnostic Challenges:
Distinguishing benign from malignant
Metastatic thyroid carcinoma exclusion
Functioning vs non-functioning
Sampling adequacy
Thyroid correlation.
Rare Variants:
Malignant struma ovarii
Papillary carcinoma arising in struma
Follicular carcinoma
Mixed with other teratomatous elements
Functioning struma.
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 mass, [side], measuring [X x Y x Z] cm
Diagnosis
Struma Ovarii, [Benign/Malignant]
Classification
WHO Classification: Monodermal Teratoma, Struma Ovarii
Histological Features
Shows thyroid follicles with colloid, [X]% of tumor volume
Special Studies
IHC: Thyroglobulin [positive], TTF-1 [positive], PAX8 [positive]
Thyroid function: [normal/hyperthyroid]
Final Diagnosis
Ovarian Struma Ovarii, [Side]