LIPOMA

Issah J. kiswagala

(M.B.B.S).

INTRODUCTION

• Lipoma is a benign tumour arising from fat cells of adult type (yellow fat).
• Tumour arising from brown fat is called as hibernoma (reddish brown).
• Lipomas are the most common soft-tissue tumour.
• It is called as universal tumour (ubiquitous tumour) as it can occur anywhere in the body where there is fat (except in brain).
• These slow-growing, benign fatty tumors form soft, lobulated masses enclosed by a thin, fibrous capsule.
• They may develop in virtually all organs throughout the body. Subcutaneous lipomas, GI tract (submucosal fatty tumors), Duodenal lipomas, Colonic lipomas, In rare instances, intraosseous and intra-articular involvement occurs.
• It can be single or multiple (5%), diffused or localised.

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EPIDEMIOLOGY�

• Lipomas occur in 1% of the population. Most of these are small subcutaneous tumors that are removed for cosmetic reasons.
• In the intestine, lipomas constitute 16% of benign, small neoplasms; this percentage is lower than that of leiomyomas (18%) and higher than that of adenomas (14%).

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AETIOLOGY/RISK FACTORS

• The exact etiology of lipomas remains uncertain, an association with gene rearrangements of chromosome 12 has been established in cases of solitary lipomas.
• A potential link between trauma and subsequent lipoma formation.

TYPES

1. Single encapsulated lipoma

• This is a single, soft, slow-growing, painless and semi-fluctuant swelling.
• Surface is lobular. Lobulations are better appreciated with firm palpation of the swelling. Due to the pressure, lobules bulge out between the fibrous tissue strands.
• The edge slips under the palpating finger which is a pathognomonic sign of Lipoma.
• Commonly present as a subcutaneous swelling. It is freely mobile.
• The flank is the commonest site. Shoulder region, neck, back, upper limbs are the other common sites. Some lipomas from the chest wall can be of large size.
• Dimpling sign: Fibrous bands connect a lipoma to the skin. When the skin moved, a dimple appears on the skin.

2. Multiple lipomatosis

• Such lipomas are multiple and very often tender because of nerve elements mixed with them. Hence, they are called multiple neurolipomatosis.
• Dercum s disease is one example of this variety (Adiposis dolorosa) wherein tender, lipomatous swellings are present in the body, mainly the trunk.

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3. Uncapsulated lipoma (diffuse)

• Diffuse variety is a rare type of lipoma. It is called pseudolipoma. It is an overgrowth of fat without a capsule.

HISTOLOGICAL TYPES OF LIPOMA

1. Fibrolipoma: Since fibrous tissue is mixed with fat, lipoma feels hard.

2. Neurolipoma: Painful Lipoma, because of presence of nerve elements.

3. Naevolipoma: Lipoma is usually relatively avascular but this variety is vascular.

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• Lipomas attain large size in thigh, shoulder, retroperitoneum, back and often may turn into sarcoma.

CLINICAL FEATURES

• Lipomas are most often asymptomatic. When they arise from fatty tissue between the skin and deep fascia, typical features include a soft, fluctuant feel; lobulation; and free mobility of overlying skin.
• A characteristic "slippage sign" may be elicited by gently sliding the fingers off the edge of the tumor. 
• Localised swelling, which is lobular, nontender.
• Semi-fluctuant (because fat in body temperature remains in semiliquid condition).
• The overlying skin is typically normal and free.
• Lipomas may be pedunculated at times.
• Symptoms in other sites depend on the location 

DIFFERENTIAL DIAGNOSES�

• Sebaceous cyst or an abscess.
• Liposarcoma
• Neurofibroma,
• Mammary hamartoma (Breast)
• Hibernomas

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INVESTIGATIONS

• For most subcutaneous lipomas, no imaging studies are required.
• Imaging studies for lipomas in atypical locations or those for which the differential diagnosis includes sarcoma include ultrasonography (US), computed tomography (CT), and magnetic resonance imaging (MRI).
• Biopsies are normally not indicated for small subcutaneous lesions, because the entire tumor is usually removed.
• FNAC/incision biopsy in suspected cases with deeply located/intracavitary lipomas/large lipomas is done.
• All imaging techniques have been combined with fine-needle aspiration (FNA); this combination increases the accuracy of diagnosis. 

TREATMENT�

Lipomas are removed for the following reasons:

• Cosmetic reasons
• To evaluate their histology, particularly when liposarcomas must be ruled out
• When they cause symptoms
• When they grow and become larger than 5 cm
• Obtain biopsies of large lipomas or of those tethered to fascia to rule out a liposarcoma.

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Treatment is Complete surgical excision.

No contraindications for removing a lipoma exist, unless the patient is unfit for surgery or anatomic location makes removal unfeasible (as in the case, for example, of an intraspinal lipoma)

• Small lipoma is excised under local anaesthesia and larger one under general anaesthesia.
• If it is liposarcoma, CT chest should be done to see secondaries in lungs. Later wide excision is done alongwith adjuvant chemotherapy and radiotherapy.

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• NOTE:

PROGNOSIS�

• The outcome and prognosis are excellent for benign lipomas. Recurrence is uncommon but may develop if the excision was incomplete.

COMPLICATIONS�

• Liposarcoma, a few retroperitoneal lipomas and lipoma in the thigh can tum into liposarcoma (Malignant) after many years of growth.
• Myxomatous degeneration: Occurs only in retroperitoneal lipoma.
• Intussusception-due to submucosal lipoma of terminal ileum is an abdominal emergency.
• Saponification
• Calcification
• Lipomas in other locations may cause luminal obstruction or hemorrhage.

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