Definition/General
Introduction:
Gastric lipoma is a benign tumor composed of mature adipose tissue
It represents less than 1% of gastric tumors
Most common location is the submucosal layer
Usually asymptomatic unless large.
Origin:
Arises from mature adipocytes in gastric wall
Most commonly from submucosal fat
Can originate from subserosal fat
Represents hamartomatous proliferation of normal fat tissue.
Classification:
Conventional lipoma (most common)
Angiolipoma (with vascular component)
Fibrolipoma (with fibrous tissue)
Atypical lipoma (well-differentiated liposarcoma)
Size-based classification: <2 cm vs >2 cm.
Epidemiology:
Peak incidence in 5th-6th decades
Female predominance (2:1 ratio)
Associated with obesity
Multiple lipomas in familial lipomatosis
Rare in children.
Clinical Features
Presentation:
Asymptomatic in small lesions (<2 cm)
Epigastric pain (30-40%)
Early satiety (20-30%)
Gastrointestinal bleeding (10-20%)
Obstruction symptoms in large lesions
Palpable mass in subserosal location.
Symptoms:
Postprandial discomfort and fullness
Nausea after meals
Chronic anemia from occult bleeding
Weight loss in obstructing lesions
Pyloric obstruction if antral location.
Risk Factors:
Obesity and metabolic syndrome
Familial multiple lipomatosis
Gardner syndrome (rare association)
Previous trauma to abdomen
Hormonal factors (estrogen).
Screening:
Upper endoscopy for symptomatic patients
CT imaging shows characteristic fat density
MRI confirms adipose tissue
Endoscopic ultrasound for small lesions
Genetic counseling for familial cases.
Master Lipoma Pathology with RxDx
Access 100+ pathology videos and expert guidance with the RxDx app
Gross Description
Appearance:
Yellow, soft mass with lobulated surface
Well-encapsulated or pseudoencapsulated
Homogeneous cut surface
Greasy consistency
Floats in formalin.
Characteristics:
Mature fat tissue appearance
Lobulated architecture
Thin fibrous septa
No areas of necrosis
Uniform yellow color throughout.
Size Location:
Size ranges from 1-10 cm (most 2-5 cm)
Antrum most common (40-50%)
Body and fundus (30-40%)
Submucosal (70%), subserosal (30%).
Multifocality:
Usually solitary (>95%)
Multiple lipomas in familial syndromes
Associated with colonic lipomas
No malignant potential.
Microscopic Description
Histological Features:
Composed of mature adipocytes with peripheral nuclei
Uniform cell size
Thin fibrous septa dividing lobules
Minimal vascular component
No lipoblasts or atypical cells.
Cellular Characteristics:
Mature fat cells with single large vacuole
Peripheral compressed nucleus
Uniform cell morphology
No nuclear atypia
No mitotic activity.
Architectural Patterns:
Lobular architecture separated by fibrous septa
Adipocytes in lobules
Capillary network between cells
Thin capsule if present.
Grading Criteria:
Benign by definition
No grading system applicable
Absence of lipoblasts
No increased cellularity
Mature adipose tissue only.
Immunohistochemistry
Positive Markers:
S-100 (weak positive)
Adipophilin (positive)
Vimentin (positive)
CD68 (macrophages present)
Perilipin (adipocyte marker).
Negative Markers:
Cytokeratins (negative)
Desmin (negative)
Smooth muscle actin (negative)
KIT (negative)
MDM2 (negative)
CDK4 (negative).
Diagnostic Utility:
Morphology usually sufficient for diagnosis
S-100 positivity supports adipose tissue
MDM2/CDK4 negativity excludes atypical lipoma
Ki-67 shows minimal proliferation.
Molecular Subtypes:
No molecular subtypes for conventional lipoma
12q13-15 amplification in atypical lipoma
Normal karyotype in conventional lipoma.
Molecular/Genetic
Genetic Mutations:
No specific mutations in conventional lipoma
12q amplification in atypical lipomatous tumor
TP53 mutations absent
Simple karyotype
Stable genome.
Molecular Markers:
Low Ki-67 (<1%)
Normal p53 expression
HMGA2 rearrangements in some cases
LPL gene normal expression.
Prognostic Significance:
Excellent prognosis
No malignant potential for conventional lipoma
Size >5 cm may cause symptoms
Complete excision curative.
Therapeutic Targets:
Surgical excision for symptomatic lesions
Endoscopic removal for small submucosal lesions
Observation for asymptomatic small lesions
No medical therapy indicated.
Differential Diagnosis
Similar Entities:
Well-differentiated liposarcoma (atypical lipomatous tumor)
Angiolipoma
Fibrolipoma
Lipoblastoma (pediatric)
Hibernoma
Lipomatosis.
Distinguishing Features:
Conventional lipoma: Mature fat, no atypia
Liposarcoma: Atypia, lipoblasts, MDM2+
Angiolipoma: Vascular component
Hibernoma: Brown fat, multivacuolar
Lipoblastoma: Pediatric, myxoid areas.
Diagnostic Challenges:
Distinguishing from well-differentiated liposarcoma
Sampling adequacy for large lesions
Recognizing degenerative changes
Clinical correlation important.
Rare Variants:
Spindle cell lipoma
Pleomorphic lipoma
Chondroid lipoma
Myolipoma (with smooth muscle)
Osteolipoma (with bone).
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
[type], [size] cm
Diagnosis
Lipoma
Features
Mature adipose tissue, no atypia
Final Diagnosis
Gastric lipoma, [size] cm, completely excised