lipoma surgery 

A lipoma is a benign neoplasm of fat cells (adipocytes) and the most common soft tissue tumor in adults. The etiology is unknown, but obesity is a predisposing factor; genetics also play a role, with multiple lipomas occurring in various inherited disorders. Lipomas can arise in any site with adipose tissue (including the gastrointestinal tract, chest cavity, retroperitoneum, and glands), but are most common in subcutaneous tissues of the trunk or proximal extremities. The treatment is not necessary for small asymptomatic lipomas. Surgical excision is the treatment if there is a cosmetic, functional, or diagnostic concern.

Overview

Definition

Lipoma is a 

benign

 neoplasm of fat cells (

adipocytes

).

Epidemiology

• The most common 
  benign
   
  soft tissue
   
  tumor
• Age: mostly adults, age > 40 years; rare in children
• Women > men
• Associated with 
  obesity
• No 
  gender
   or ethnic preference
• Multiple lipomas account for 5% of cases:
  • Often familial
  • Often associated with genetic disorders

Etiology

• Unknown for most lipomas
• Genetics
   in some cases:
  • Solitary lipomas: HMGA2-LPP fusion 
    gene
     defect in 
    chromosome
     12
  • Some are associated with genetic syndromes:
    • Familial multiple lipomatosis
    • Adiposis dolorosa
    • Neurofibromatosis
    • Multiple endocrine neoplasia
    • Gardner’s syndrome
    • Madelung’s disease
    • Bannayan-Riley-Ruvalcaba syndrome
• Environmental factors:
• Obesity
   (definite)
• Possible factors:
• Diabetes
   and other endocrine disorders
• Trauma
• Radiation
• Corticosteroid therapy

Pathophysiology and Clinical Presentation

Pathophysiology

Anatomic sites:

• Benign
   neoplasm composed of mature 
  adipose cells
• Can arise in any site where there is 
  adipose tissue
  :
  • Most arise in 
    subcutaneous tissue
    , on the trunk or upper extremities
  • Submucosal gastrointestinal sites, from the 
    esophagus
     to the lower intestine
  • Less common sites:
    • Retroperitoneal
    • Intraglandular
    • Intramuscular 
    • Parosteal lipoma

Morphology:

• Size:
  • Usually 2–3 cm
  • Range from < 1 cm to > 10 cm, especially if in deeper tissues
• Single most common, but may be multiple
• Soft, rubbery
• Mobile (not fixed to surrounding tissues)
• Round, oval, or multi-lobulated
• Bright yellow 
  homogeneous
   fat with a fine 
  fibrous capsule
   (superficial lesions) and trabeculae
• Greasy cut surface

Histology:

• Mature 
  adipose tissue
  , with 
  adipocytes
   showing no 
  atypia
  , but 2–5x variation in cell size
• Lobular architecture with thin septae
• No mitotic figures
• Scant vascularity
• Thin 
  fibrous capsule
• Fat 
  necrosis
  :
  • More likely in larger lipomas
  • Focal, with 
    histiocytes
     +/- calcification
• Some histologic variants:
• Angiolipoma
  :
  • Small, well-circumscribed, subcutaneous 
    tumor
  • Mature 
    adipose cells
    , capillary vessels with 
    fibrin
     thrombi
  • Angiolipoma
     is 1 of 5 of the most common painful 
    skin
     tumors. (The other 4 are: neuroma (traumatic), glomus 
    tumor
    , eccrine spiradenoma, and 
    leiomyoma
     (vascular), creating the mnemonic “ANGEL.”)
• Fibrolipoma
• Chondroid lipoma
• Ossifying lipoma     

Clinical Presentation

• Subcutaneous lipomas (most common):
  • 2–3 cm (can be > 10 cm) soft, mobile 
    mass
    , usually on the trunk or upper extremities
  • Usually solitary 
  • Painless
  • No overlying 
    skin
     changes
  • Can occur anywhere on the body
• Gastrointestinal lipomas:
  • Intestinal obstruction
     or 
    intussusception
     (
    nausea
    /
    vomiting
    , 
    abdominal pain
    )
  • Gastrointestinal hemorrhage
     (from mucosal 
    ulceration
    )
• Other sites, e.g. retroperitoneum, body cavities: 
  compression
   effects on adjacent organs

diagnosis and Management

Diagnosis

History:

• A slowly growing lump (usually painless) for subcutaneous lipomas
• For other types of lipomas reported, symptoms depend on the site.
• Family history
  /genetic disorders

Physical exam:

• Soft, rubbery, mobile 
  nodule
• “Slippage sign”: 
  Tumor
   will slip out from under the fingers.
• Deeper or intramuscular lipomas may present as 
  swelling
  .

Imaging:

• Not required for most subcutaneous lipomas
• Ultrasound (US):
  • Can be used for subcutaneous lesions with atypical appearance
  • For deep 
    soft tissue
     or 
    retroperitoneal
     lesions
• Computed tomography (CT):
  • Density < 50 
    Hounsfield units
     is indicative of a fatty 
    tumor
  • However, cannot reliably distinguish lipoma from liposarcoma
• Magnetic resonance imaging (MRI): also cannot reliably rule out 
  malignancy

Endoscopy

 and endoscopic ultrasound (EUS):

• From the 
  esophagus
   to the 
  colon
• Appear as smooth, round submucosal nodules
• Possible mucosal 
  ulceration
   if large
• EUS can help confirm the diagnosis of a lipoma.

Biopsy

:

• If diagnosis is uncertain and 
  malignancy
   suspected
• Core needle (for deep/
  retroperitoneal
   lesions)
• Incisional 
  biopsy
   is an option for large 
  soft tissue
   lesions.

Management

Expectant management: appropriate for small (< 5 cm) subcutaneous asymptomatic lipomas

Surgical excision:

• Subcutaneous lipomas:
  • Indications:
    • Pain
       
    • Cosmesis
    • Diagnosis in doubt
    • Increase in size
  • Excision needs to involve the 
    fibrous capsule
     to reduce recurrence. 
• Gastrointestinal lipomas:
  • Surgical resection if symptomatic/obstructive
  • Endoscopic removal may be feasible if small. 
• Other sites (retroperitoneum, intraglandular):
  • Resection usually needed if 
    malignancy
     is in question
  • Always needed if symptomatic
  • Biopsy
     prior to resection, if feasible.

Complications of surgery:

• Scarring
• Seroma formation
• Hematoma
   formation
• Infection