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]