Lipoma

By Dr Mohammad Manzoor Mashwani

Lipoma- a benign tumor of adipose tissue

• Lipomas are slow growing benign tumors of adipose tissue, which may remain stationary or grow slow.

• They are the most common tumors of adulthood. Most are solitary lesions; multiple lipomas usually suggest the presence of rare autosomal dominant syndromes.

• Lipomas are soft in consistency, mobile and generally painless except angiolipomas .

• They are commonly found in adult 40-60 years of age but can also be found in children.

TYPESThere are several subtypes of lipomas based on

histological features.

1. Conventional Lipomas

2. Angiolipomas

3. Myolipoma

4. Pleomorphic lipomas

5. Spindle cell lipomas6. Fibrolipoma

7. Myelolipoma

The most common type is conventional lipomas.

Mnemonic:Camps

Traumatic LipomaGiant Lipoma

• Neck lipoma (lipoma on neck) – A patient may want to remove a neck lipoma for cosmetic reasons.• Breast lipoma – While benign, any lumps found in the breasts should be examined by a doctor to rule out cancer.• Forehead lipoma (lipoma on forehead) – Typically, these do not need to be removed for medical reasons, but

patient may want to have them removed for cosmetic reasons.• Spinal lipoma (lipoma on spine) – Also known as a filum terminale lipoma or filum lipoma, spinal lipomas may

need to be removed because they can be painful and result in other symptoms such as numbness, tingling, weakness, urinary incontinence, stiffness in the hands and feet, and difficulty with bowel movements.

• Head lipoma (lipoma on head or scalp lipoma) – While rare, a scalp lipoma can be painful or irritating, however having this type of lipoma removed is a fairly easy and quick procedure.

• Back lipoma (lipoma on back or lower back) – Also known as an episacral lipoma or episacroiliac lipoma, these lipomas do not typically need to be removed except for cosmetic reasons or if they are causing lower back pain.

• Abdominal lipoma – These occur either as a result of a genetic mutation or a hereditary condition called lipomatosis.

• Shoulder lipoma – The shoulder is an extremely common spot for lipomas to form.• Arm lipoma (lipoma on arm) – One of the most common places for lipomas to develop is the arm.• Thigh lipoma (lipoma on thigh) – Another one of the most common lipoma formation spots is the thigh.• Chondroid lipoma – Chondroid lipomas are yellow and deep-seated, and typically occur in the legs of women.• Spindle cell lipoma – Asymptomatic, these lipomas are most often found among older men in the back, neck and

shoulders.

• Common internal lipomas include:• Brain lipoma (corpus callosum lipoma) – These may or may not present symptoms, and are

considered a rare congenital brain condition.• Kidney lipoma (renal lipoma) – Kidney lipomas typically occur in middle-aged women• Colon lipoma (submucosal lipoma) – These lipomas are very rare and are most often detected

through a colonoscopy.• Pancreatic lipoma – These rare lipomas are most often detected incidentally through CT scans.• Spermatic cord lipoma – Fairly rare, spermatic cord lipomas typically present with hernia-like

symptoms• Pedunculated lipoma – These occur in the gastrointestinal tract (sometimes as a duodenal lipoma).• Intramuscular lipoma – Developing in muscle tissue, intramuscular lipomas usually form within the

neck, legs, head and torso.• Lipoma arborescens – This is a rare condition that affects the joints, and may cause joint swelling.• Intraosseous lipoma – This extremely rare lipoma affects the bones, typically within the lower

extremities.

A variety of admixture of lipoma with other tissuecomponents may be seen.

These include:

Fibrolipoma (admixture with fibrous tissue),

Angiolipoma (combination with proliferating blood vessels) and

Myelolipoma (admixture with bone marrow elements as seen in adrenals).

Infrequently, benign lipoma may infiltrate the striated muscle (infiltrating or intramuscular lipoma).

Spindle cell lipoma and

pleomorphic (atypical) lipoma are the other unusual variants of lipoma.

The latter type may be particularly difficult to distinguish from well-

differentiated liposarcoma.

• Mostly occurs on proximal extremities, neck, back & shoulder but can occur anywhere in the body where fat is present.

Lipomas are usually relatively small with diameters of about 1-3 cm but in rare cases they can grow to a very large size 10 to 20 cm in size. “Giant lipomas”.

A lipoma rarely ever transforms into liposarcoma.

PREVALENCE

• Prevalence is 1% in general population.

• Most common at the age of 40-60 years and are frequent in females.

• There may be hereditary predisposition to development of lipomas, Familial multiple lipomatosis.

• It is also believed that lipomas can also occur as a result of trauma. Such lipomas are called traumatic lipomas.

MORPHOLOGY: ( CONVENTIONAL)

GROSS:Location: any, upper extremities, neck, back & shoulder.

Size: 1-3 cm

Number: solitary

Shape: round to oval

Consistency: Soft

Mobile

Nontender & painless

Well encapsulated masses of fat present in superficial soft tissues.

Cut surface is lobulated and shows bright yellow fatseparated by fine fibrous septae.

Microscopy

• Microscopically it is composed of an encapsulated mass of mature and uniform size adipocytes, without any cellular atypia. Fibrous septae are traversing through the mass of tumors.

Diagnostic points:

1. There is fibrous capsule present.

2. Fibrous septa can be seen traversing through adipocytes.

Diagnostic points:

On histopathology the features which differentiate the lipoma from normal adipose tissue are:-

There is fibrous capsule present.

Fibrous septa can be seen traversing through adipocytes.

Lipoma. Common clinical location.

The cut surface of the tumour is soft, lobulated, yellowish and greasy.

Normal Adipose tissue

Lipoma

LIPOSARCOMA

Liposarcoma is one of the most common soft tissuesarcomas in adults, perhaps next in frequency only tomalignant fibrous histiocytoma. Unlike lipoma whichoriginates from mature adipose cells, liposarcoma arisesfrom primitive mesenchymal cells, the lipoblasts. The peakincidence is in 5th to 7th decades of life. In contrast tolipomas which are more frequently subcutaneous inlocation, liposarcomas often occur in the deep tissues. Mostfrequent sites are intermuscular regions in the thigh,buttocks and retroperitoneum.

Morphology

Grossly, liposarcoma appears as a nodular mass, 5 cm or more in diameter. The tumour is generally circumscribed but infiltrative. Cut surface is grey-white to yellow, myxoid and gelatinous. Retroperitoneal masses are

generally much larger.

Histologically, the hallmark of diagnosis of liposarcoma

is the identification of variable number of lipoblasts which may be univacuolated or multivacuolated. The vacuoles represent fat in the cytoplasm.

Four major histologic varieties of liposarcomas are distinguished:well-differentiated, myxoid, round cell, and pleomorphic.1. Well-differentiated liposarcoma resembles lipoma butcontains uni- or multi-vacuolated lipoblasts.2. Myxoid liposarcoma is the most common histologic type.It is composed of monomorphic, fusiform or stellate cellsrepresenting primitive mesenchymal cells, lying dispersedin mucopolysaccharide-rich ground substance. Occasionaltumour giant cells may be present. Prominent meshworkof capillaries forming chicken-wire pattern is aconspicuous feature. 3. Round cell liposarcoma is composed of uniform, roundto oval cells having fine multivacuolated cytoplasm withcentral hyperchromatic nuclei. Round cell liposarcomamay resemble a signet-ring carcinoma but mucin stainshelp in distinguishing the two.4. Pleomorphic liposarcoma is highly undifferentiated andthe most anaplastic type. There are numerous largetumour giant cells and bizarre lipoblasts.

The prognosis of liposarcoma depends upon the location

and histologic type. In general, well-differentiated and

myxoid varieties have excellent prognosis, while

pleomorphic liposarcoma has significantly poorer prognosis.

Round cell and pleomorphic variants metastasisefrequently

to the lungs, other visceral organs and serosal surfaces.