Histopathology of Lipoma

1. Lipoma
By
Dr Mohammad Manzoor Mashwani

2. 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.

8. TYPES
There are several subtypes of lipomas based on
histological features.
1. Conventional Lipomas
2. Angiolipomas
3. Myolipoma
4. Pleomorphic lipomas
5. Spindle cell lipomas
6. Fibrolipoma
7. Myelolipoma
The most common type is conventional
lipomas.
Mnemonic:Camps
Traumatic Lipoma
Giant Lipoma

9. • 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.

10. • 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.

11. A variety of admixture of lipoma with other tissue
components 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.

12. • 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.

13. 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.

14. 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 fat
separated by fine fibrous septae.

15. 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 capsulepresent.
2. Fibrous septa can be seen traversing through adipocytes.

16. 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.

17. Lipoma. Common clinical location.

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

19. Normal Adipose tissue

21. Lipoma

22. LIPOSARCOMA
Liposarcoma is one of the most common soft tissue
sarcomas in adults, perhaps next in frequency only to
malignant fibrous histiocytoma. Unlike lipoma which
originates from mature adipose cells, liposarcoma arises
from primitive mesenchymal cells, the lipoblasts. The peak
incidence is in 5th to 7th decades of life. In contrast to
lipomas which are more frequently subcutaneous in
location, liposarcomas often occur in the deep tissues. Most
frequent sites are intermuscular regions in the thigh,
buttocks and retroperitoneum.

23. 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.

24. 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.

26. Four major histologic varieties of liposarcomas are distinguished:
well-differentiated, myxoid, round cell, and pleomorphic.
1. Well-differentiated liposarcoma resembles lipoma but
contains uni- or multi-vacuolated lipoblasts.
2. Myxoid liposarcoma is the most common histologic type.
It is composed of monomorphic, fusiform or stellate cells
representing primitive mesenchymal cells, lying dispersed
in mucopolysaccharide-rich ground substance. Occasional
tumour giant cells may be present. Prominent meshwork
of capillaries forming chicken-wire pattern is a
conspicuous feature.
3. Round cell liposarcoma is composed of uniform, round
to oval cells having fine multivacuolated cytoplasm with
central hyperchromatic nuclei. Round cell liposarcoma
may resemble a signet-ring carcinoma but mucin stains
help in distinguishing the two.
4. Pleomorphic liposarcoma is highly undifferentiated and
the most anaplastic type. There are numerous large
tumour giant cells and bizarre lipoblasts.

27. 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 metastasise
frequently
to the lungs, other visceral organs and serosal surfaces.