Lipoma in A Forearm

A lipoma is the commonest and most benign of all tumours. It is composed of fat cells of adult type. It can occur anywhere in the body, that is why it is often called ‘universal tumor’ or ‘ubiquitous tumour’.

But the common sites are the subcutaneous tissue of

• The trunk
• Nape of the neck
• The limbs.

Varieties: Mainly there are three varieties

• Encapsulated lipoma
• Diffuse lipoma
• Multiple lipomas:

Diffuse Lipoma

This is a rare variety and does not possess the typical features of lipoma, hence it is often called ‘pseudolipoma’. It is seen in the subcutaneous and intermuscular tissues of the neck. It is not a typical tumour but an overgrowth of the fat in this region.

It does not possess the capsule which is typical of a lipoma. It gives rise to a disfiguring swelling at the neck. It is often found in persons taking excessive alcohol.

Treatment is excision of the excess of fat if it is required by the patient due to cosmetic reason.

Multiple lipomas:

Such variety is not uncommon. It is often called lipomatosis. The tumours remain small or moderate in size and are sometimes painful as these often contain nerve tissue and are called neurolipomastosis. These are mostly seen in the limbs and in the trunk.

Lipomata of different sizes and shapes may be seen. Macroscopically and microscopically these are not different from solitary lipoma. Dercum’s disease (adivosis dolorosa) is a variety of this condition in which there are tender lipomatous swellings particularly affecting the trunk.

A few lipomas may contain other tissues and names accordingly-

1. Fibrolipoma – when a lipoma contains an excessive amount of fibrous tissue.
2. Naevolipoma – when a lipoma contains excessive vascularity with telangiectasis of the overlying skin.
3. Neurolipoma – when a lipoma contains nerve tissue. It is often painful.

Complication

A lipoma when present for a long time may undergo certain changes. This is particularly true in case of lipoma in the subcutaneous tissue of the thigh, buttock or a retroperitoneal lipoma. Such changes are: (i) Myxomatous degeneration (ii) Saponification (iii) Calcification (iv)malignant or sarcomatous change. Though liposarcoma is not uncommon, yet a lipoma turning into liposarcoma is not so common.

Clinically a lipoma can occur in different anatomical situations.

According to this a lipoma can be classified into-

1. Subcutanous type: This is the commonest variety. Although any part of the body can be affected, yet it shows particular tendency to occur in the back, nape of the neck and on the shoulders. Subcutaneous lipoma is usually sessile, but occasionally may become pedunculated. The characteristic features of such lipoma are described below.
2. Subfascial lipoma: Lipoma may occur under the palmar or plantar fascia and is often mistaken as tuberculous tenosynovitis. Such lipomas may also occur in the areolar layer under the epicranial aponeurosis in the scalp. Subfascial lipoma can be confused with a dermoid cyst, particularly so, as such lipoma may also erode the underlying bone as the dermoid cyst. Treatment is urgent excision of the tumour.
3. Intermuscular lipoma: Such lipoma occurs between the adjacent muscles and becomes firmer on feel when the adjacent muscles contract. Mechanical interference with the action of the muscles is often complained of. Fibrosarcoma is also common in such situation and is difficult to differentiate from this condition clinically. Intermuscular lipoma is mostly seen in the thigh or around the shoulder. Treatment is early excision as it is difficult to differentiate from fibrosarcoma.
4. Subserous lipoma: This is rare and is sometimes found beneath the pleura or peritoneum. When it is beneath the pleura it presents as a benign thoracic tumour. Retroperitoneal lipoma is also rare and is often misdiagnosed as hydronephrosis, pancreatic cyst or teratomatous cyst. A retroperitoneal lipoma may attain a big size. Very occasionally one may find a lipomatous mass rather than a lipoma at the fundus of the sac of a femoral hernia. This is a condensation of extraperitoneal fat rather than a typical lipoma.
5. Submucous lipoma – is also rare. It may occur in the respiratory or elementary tract. It is also seen in the tongue. In the respiratory tract it may cause respiratory obstruction. In the intestine it may lead to intussusception.
6. Intra-articular – inside the joint. It is extremely rare.
7. Subsynovial lipoma – such lipoma occurs deep to the synovial membrane in the fatty pad. It is seen in the knee joint. In this case it is often compared with Baker s cyst or a bursitis.
8. Parosteal lipoma - occurs under the periosteum of a bone
9. Extradural lipoma: This is a type of spinal tumour. Intracranial lipoma does not occur as there is no fat in the extradural tissue within the skull.
10. Intraglandular lipoma: There are 3 glands in which a lipoma may be seen (i) the breast (ii) the pancreas and (iii) under the renal capsule.