Definition/General
Introduction:
Ovarian fibroma is the most common benign sex cord-stromal tumor
Accounts for 4-5% of all ovarian tumors
Composed of mature fibrous tissue
May be associated with Meigs syndrome (ascites and pleural effusion).
Origin:
Originates from ovarian stromal cells with fibroblastic differentiation
Shows mature fibrous tissue formation
Contains spindle-shaped fibroblasts
Abundant collagen production.
Classification:
Typical fibroma (>90%)
Cellular fibroma (increased cellularity)
Fibroma with minor sex cord elements
Fibrosarcoma (rare malignant)
Sclerosing stromal tumor (variant).
Epidemiology:
Peak incidence in postmenopausal women (5th-6th decade)
Mean age 48 years
Unilateral in 90% cases
Bilateral in 10%
Associated with Gorlin syndrome (multiple fibromas).
Clinical Features
Presentation:
Asymptomatic pelvic mass (50%)
Abdominal/pelvic pain (40%)
Meigs syndrome (1%) with ascites and pleural effusion
Abdominal distension
No hormonal effects.
Symptoms:
Pelvic mass (60-70%)
Abdominal pain (40-50%)
Abdominal distension (30%)
Dyspnea (if pleural effusion)
Weight gain (ascites)
Asymptomatic (30-40%).
Risk Factors:
Postmenopausal age
Gorlin syndrome (nevoid basal cell carcinoma syndrome)
Family history (rare)
No established hormonal factors
Environmental factors unclear.
Screening:
Pelvic ultrasound (solid hypoechoic mass)
CT/MRI (low signal intensity)
CA-125 (may be elevated)
Tumor markers usually normal
Chest X-ray (pleural effusion assessment).
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Gross Description
Appearance:
Solid, well-circumscribed mass
White to gray cut surface
Whorled appearance
Size ranges from 1-30 cm (average 6 cm)
Firm to hard consistency.
Characteristics:
Unilateral in 90% cases
Smooth capsule
Cut surface shows white fibrous tissue
Whorled pattern
Hard consistency
No hemorrhage or necrosis typically.
Size Location:
Variable size (0.5-40 cm)
Average size 5-8 cm
No specific ovarian location preference
Larger tumors more likely to cause symptoms
Slow growth pattern.
Multifocality:
Usually unifocal
Multiple fibromas in Gorlin syndrome
Bilateral involvement in 10%
No metastatic potential.
Microscopic Description
Histological Features:
Mature spindle cells in fascicles
Abundant collagen between cells
Storiform pattern
Hyalinized areas common
Calcifications may be present.
Cellular Characteristics:
Spindle-shaped cells with elongated nuclei
Bland nuclear features
Eosinophilic cytoplasm
Low cellularity
Rare mitoses (<4/10 HPF).
Architectural Patterns:
Fascicular pattern
Storiform (whorled) pattern
Interlacing bundles
Hyalinized areas
Edematous areas (cellular variant).
Grading Criteria:
Benign fibroma: <4 mitoses/10 HPF
Cellular fibroma: increased cellularity, <4 mitoses/10 HPF
Fibrosarcoma: >4 mitoses/10 HPF, significant atypia.
Immunohistochemistry
Positive Markers:
Vimentin (100%)
Smooth muscle actin (focal, 30%)
CD34 (variable)
Desmin (focal, rare)
Reticulin (surrounds individual cells).
Negative Markers:
Inhibin (negative)
Calretinin (negative)
Cytokeratin (negative)
EMA (negative)
S-100 (negative)
CD117 (negative).
Diagnostic Utility:
Vimentin positivity confirms mesenchymal origin
Negative sex cord markers (inhibin, calretinin)
Distinguish from thecoma and granulosa cell tumor
Smooth muscle actin may be focally positive.
Molecular Subtypes:
PTCH1 mutations (Gorlin syndrome cases)
Low mutation burden
Chromosomal stability
Different from uterine fibroids
MED12 mutations rare.
Molecular/Genetic
Genetic Mutations:
PTCH1 mutations (Gorlin syndrome)
Sporadic cases - few mutations
Chromosomal stability
Low somatic mutation rate
Different from leiomyomas.
Molecular Markers:
Collagen gene expression
Fibroblast markers
Low proliferation (Ki-67 <5%)
p53 wild-type
Stable karyotype.
Prognostic Significance:
Excellent prognosis
No malignant potential (typical fibroma)
Cellular fibroma - excellent prognosis
Size >10 cm - higher recurrence if incompletely excised.
Therapeutic Targets:
Surgical excision curative
Enucleation possible for benign cases
Oophorectomy for large tumors
No adjuvant therapy needed.
Differential Diagnosis
Similar Entities:
Thecoma (lipid-rich cells, inhibin positive)
Fibrothecoma (mixed features)
Leiomyoma (smooth muscle markers)
Sclerosing stromal tumor (younger patients)
Metastatic carcinoma.
Distinguishing Features:
Fibroma: Pure spindle cells
Inhibin negative
Thecoma: Lipid-rich cells
Inhibin positive
Leiomyoma: Smooth muscle actin strong
Desmin positive
Sclerosing stromal: Pseudolobular pattern
Younger patients.
Diagnostic Challenges:
Fibroma vs thecoma distinction
Cellular fibroma vs fibrosarcoma
Mitotic count assessment
Sampling adequacy
Gorlin syndrome association.
Rare Variants:
Cellular fibroma
Fibroma with minor sex cord elements
Calcifying fibrous tumor
Fibrosarcoma (malignant)
Multiple fibromas (Gorlin syndrome).
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
Fibroma, [Typical/Cellular]
Classification
WHO Classification: Sex Cord-Stromal Tumor, Fibroma
Histological Features
Shows spindle cells in fascicles with abundant collagen
Mitotic Activity
Mitoses: [X]/10 HPF (benign range <4/10 HPF)
Special Studies
IHC: Vimentin [positive], Inhibin [negative], Calretinin [negative]
Final Diagnosis
Ovarian Fibroma, [Side]