Definition/General
Introduction:
Fibroma is a benign fibroblastic tumor
It represents mature fibrous tissue proliferation
Accounts for 5-10% of soft tissue tumors
FNAC shows bland spindle cells with collagen.
Origin:
Arises from fibroblasts and myofibroblasts
Develops from reactive fibrous tissue or true neoplasm
Can occur in skin, subcutis, or deep soft tissue
Associated with trauma or chronic irritation.
Classification:
WHO classification: Benign fibroblastic tumor
Types include: Soft fibroma (fibroma molle)
Hard fibroma (dermatofibroma)
Nuchal fibroma
Plantar fibroma
Palmar fibroma.
Epidemiology:
Can occur at any age
No gender predilection for most types
Common benign tumor
Plantar fibroma: Middle-aged adults
Associated with diabetes mellitus (palmar/plantar).
Clinical Features
Presentation:
Slow-growing nodule
Painless in most cases
Well-circumscribed mass
Firm consistency
Mobile (superficial lesions)
Skin-colored or slightly hyperpigmented.
Symptoms:
Usually asymptomatic
Pain in plantar fibroma (walking)
Functional impairment (large lesions)
Cosmetic concern
Contracture (palmar fibroma)
Pressure symptoms.
Risk Factors:
Chronic trauma
Repetitive injury
Diabetes mellitus (palmar/plantar)
Dupuytren disease association
Genetic predisposition (some families)
Age >40 years.
Screening:
Clinical examination for nodules
Palpation for consistency
FNAC for diagnosis
Imaging for deep lesions
Family history assessment
Blood glucose screening.
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Gross Description
Appearance:
Well-circumscribed nodule
Firm to hard consistency
Gray-white cut surface
Whorled pattern
Homogeneous appearance
No necrosis.
Characteristics:
Encapsulated or well-demarcated
Dense fibrous consistency
White to gray color
Glistening surface
Fascicular pattern
Uniform texture.
Size Location:
Skin and subcutis most common
Hands and feet
Back of neck (nuchal fibroma)
Plantar surface (plantar fibroma)
Size: 0.5-5 cm typically
Deep soft tissue (rare).
Multifocality:
Usually solitary
Multiple lesions in some syndromes
Bilateral plantar fibroma possible
Associated with contractures
Familial clustering (rare).
Microscopic Description
Histological Features:
FNAC shows bland spindle cells
Elongated nuclei
Sparse cellularity
Abundant collagen
No cellular atypia
Minimal mitotic activity.
Cellular Characteristics:
Uniform spindle cells
Oval to elongated nuclei
Fine chromatin
Inconspicuous nucleoli
Scanty cytoplasm
Well-defined cell borders.
Architectural Patterns:
Paucicellular smears
Collagenous background
Scattered spindle cells
Fascicular arrangement
Dense fibrous tissue
Clean background.
Grading Criteria:
Benign cytological features
No grading system applicable
Assessment: Cellular uniformity
Absence of atypia
Low cellularity
Mature fibroblastic features.
Immunohistochemistry
Positive Markers:
Vimentin - positive
CD34 - variable (some cases)
Smooth muscle actin - focal positive
Muscle-specific actin - variable
Factor XIIIa - may be positive
Procollagen - positive.
Negative Markers:
S-100 protein - negative
Desmin - negative
Cytokeratin - negative
EMA - negative
CD68 - negative
MyoD1 - negative.
Diagnostic Utility:
Vimentin confirms mesenchymal origin
Variable CD34 expression
SMA may be positive (myofibroblastic differentiation)
Ki-67 very low (<1%)
Negative neural markers.
Molecular Subtypes:
Conventional fibroma: Vimentin+, CD34 variable
Myofibroma: SMA+, desmin variable
Dermatofibroma: Factor XIIIa+, CD68+
Nuchal fibroma: CD34-, EMA-.
Molecular/Genetic
Genetic Mutations:
Simple karyotype in most cases
No specific mutations identified
Clonal proliferation in some cases
Reactive hyperplasia in others
Chromosomal stability.
Molecular Markers:
Low proliferation markers
Collagen synthesis markers positive
TGF-β pathway activation
Fibroblastic markers
Normal p53
Intact tumor suppressors.
Prognostic Significance:
Excellent prognosis
No malignant potential
Local recurrence <5% after complete excision
No metastatic risk
May recur if incompletely excised.
Therapeutic Targets:
Complete surgical excision
No adjuvant therapy required
Observation for small lesions
Physical therapy (contractures)
Steroid injection (selected cases).
Differential Diagnosis
Similar Entities:
Fibrosarcoma
Nodular fasciitis
Fibromatosis
Neurofibroma
Dermatofibrosarcoma protuberans
Solitary fibrous tumor.
Distinguishing Features:
Fibroma: Bland spindle cells, low cellularity, mature collagen
Fibrosarcoma: Cellular atypia, high mitoses, necrosis
Nodular fasciitis: High cellularity, rapid growth
Fibromatosis: Infiltrative, nuclear β-catenin
Neurofibroma: S-100+, wavy nuclei
DFSP: CD34+ uniform, infiltrative.
Diagnostic Challenges:
Distinguishing from low-grade fibrosarcoma
Fibromatosis vs fibroma
Reactive vs neoplastic
Sampling adequacy in paucicellular lesions
Site-specific variants.
Rare Variants:
Giant cell fibroma
Pleomorphic fibroma
Ossifying fibroma
Myxoid fibroma
Sclerotic fibroma.
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
Fine needle aspiration from [site], [size] cm firm nodule
Clinical History
[age]/[sex] with [duration] history of slow-growing firm nodule at [site]
Microscopic Examination
Paucicellular smears showing scattered bland spindle cells with elongated nuclei and scanty cytoplasm. Background shows abundant collagenous material. No cellular atypia or mitotic activity.
Cytological Diagnosis
Cytological features consistent with FIBROMA
Comments
Benign fibroblastic lesion. Complete excision if symptomatic. Excellent prognosis. Clinical correlation recommended.