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Soft tissue tumors of the skin, benign (lipoma, fibroma, atheroma)

Basics
Causes
Symptoms
Diagnosis
Forecast
Swelling, without pain
Lumps under the skin
reddened, swollen skin areas
genetic predisposition
obstruction of an excretory duct
Nerve injuries
high blood lipid levels
surgical procedure

Basics

Soft tissue tumors are tumors of different tissues (fatty tissue, connective tissue, nervous tissue, musculature). The majority of these tumors are benign. Soft tissue tumors are relatively common in the population. The term "tumor" does not indicate whether it is benign or malignant, but merely refers to a swelling or new tissue formation.

Different types of soft tissue tumors can be distinguished:

  • Lipoma: Benign neoplasm of fatty tissue.

  • Fibroma: Benign neoplasm of the connective tissue

  • Atheroma (gout sac): Accumulation of dead skin cells and sebum near a sebaceous gland.

In addition, there are some rarer soft tissue tumors:

  • Neurofibroma: neoplasm of the supporting tissue of the peripheral nervous system (Schwann cells) that is benign.

  • Acanthoma: Benign neoplasm of the prickle cells of the skin.

  • Neuroma: Usually occurring after nerve injury, benign neoplasm containing nerve cells, nerve fibers and connective tissue.

Ein Lipom am Handgelenk (iStock / taniche)

Lipom

Lipoma is a common benign adipose tissue tumor. Lipomas grow with a slow growth in most cases only a few centimeters in size. However, in rare cases, they can grow into a giant lipoma (with a diameter of more than 5 cm). When a lipoma is crossed by blood vessels, it is also called angiolipoma. In more than 50% of cases, several angiolipomas occur at the same time - this special form is most common in young men. Generally, lipomas occur in people over 30 years of age and are often located under the skin. Regions of the body where lipoma frequently occurs are the trunk, neck, and shoulder-arm region. However, lipomas can also occur in muscles, abdominal organs, and bone. If a lipoma occurs in the head region, it may be located under the connective tissue layer, or subfascial, and is then called a subfacial lipoma. In addition to the head area, subfascial lipomas can also occur in the neck or shoulder blade area. The so-called spindle cell lipoma is a special form that usually occurs on the back, neck or in the area of the shoulders in men between 45 and 60 years of age.

Fibroma:

The formation of new connective tissue (fibroma) involves certain groups of connective tissue cells called fibrocytes. In this context, fibromas are small, benign tumors. Malignant connective tissue tumors are also called fibrosarcomas. Fibromas are divided into different forms:

A) Soft fibroma:

Soft fibroma is also known as fibroma molle or fibroma pendulans. The skin-colored, small (a few millimeters in size) skin protrusions that develop are equally common in both women and men. Soft fibromas often first appear at puberty. They can either rest on the skin with a broad base or be pedunculated (narrow base and broader "head"). Because of their pedunculated appearance, soft fibromas are also called pedunculated warts. Common areas of the body include the neck, armpits, and groin. Soft fibromas can occur singly or in groups.

B) Hard fibroma:

Hard fibroma, also called histiocytoma or dermatofibroma, occurs in most adults, with the most common location being on the legs (followed by the arms and trunk). Hard fibromas, unlike soft fibromas, are firmer nodules a few millimeters in size. In rare cases, a hard fibroma can grow up to one centimeter and become visible as a dark or light brown spot in the skin.

C) Irritant fibroma:

An irritation fibroma or irritation fibroma forms smooth, small nodules on the oral mucosa. This expression can occur with persistent irritation of certain areas in the mouth.

D) Other fibromas:

Other rare connective tissue cell tumors include:

  • Ossifying fibroma: benign tumor on the facial skull or mandibular bone, respectively.

  • Non-ossifying fibroma: connective tissue change of the bone occurring in children.

  • Chondromyxoid fibroma: Tumor in long bones occurring primarily in adolescents.

  • Desmoplastic fibroma: A rapidly growing bone tumor occurring primarily in young people.

  • Angiofibroma: Tumor in nasopharynx with vessels occurring primarily in adolescent males.

Atheroma:

An atheroma, colloquially known as a gruel pouch, is a cavity in the subcutaneous tissue filled with skin cells and fat. Atheromas can form due to clogged sebaceous glands and are benign horny cysts of the skin. Atheromas often develop at the hair root, which is why body parts with a lot of hair are increasingly affected by atheromas (90% on the scalp). Non-inflamed atheromas can reach a size of one to two centimeters. In case of inflammation, they can grow up to the size of a chicken egg (rarely larger).

Epidermoid cysts and trichilemmal cysts

Atheromas can be divided into epidermoid cysts and trichilemmal cysts. Epidermal cysts are non-painful, bulging elastic nodules of the skin. They have an excretory duct connected to the skin surface and grow slowly. Most often they occur on the face or back. If an epidermal cyst becomes inflamed or infected, surgical removal is often necessary. Trichilemmal cysts, unlike epidermal cysts, do not have a central excretory duct. Their contents are firm, hard, odorless, and they almost always occur in groups. If the trichilemmal cyst bothers affected persons visually or it causes discomfort, surgical removal is recommended.

Rarely occurring malignant soft tissue tumors are called soft tissue sarcomas or malignant soft tissue tumors.

Causes

The exact mechanism of the development of soft tissue tumors is still largely unknown. Most likely, however, a hereditary predisposition plays a role in the development.

Schematischer Aufbau eines Lipoms (iStock / ttsz)

Lipoma:

At least 1% of the population will develop a lipoma once in their lifetime. In adults, lipomas account for about one third of all benign soft tissue tumors. A genetic predisposition as a cause has not yet been clearly proven for single lipomas. Also, many lipomas that occur simultaneously (lipomatosis) have not yet shown a clear trigger. Lipomatosis often occurs in patients with metabolic disorders such as diabetes mellitus or hyperuricemia. It is possible that excessively high blood lipid levels may be involved in the development of lipomas.

Fibroma:

The cause of fibroma development is still unknown.

Atheroma:

The reason for the development of a gout (atheroma) is a blocked excretory duct of a sebaceous gland. Starting from this blockage, secretion backs up. Atheromas therefore consist of fat droplets, fat crystals and skin cells.

Neuroma:

The cause of neuroma is nerve injury. Similar to the mechanism in excessive wound healing with scarring, the injured nerve attempts to bridge its damage with sprouting. If this attempt fails, a neuroma is formed.

Symptoms

A characteristic symptom of a benign soft tissue tumor is usually painless swelling. However, pain may occur in unfavorable localizations - for example, near nerves. Benign soft tissue tumors are generally characterized by good displaceability against the surrounding tissue. They are well demarcated, so to speak.

Lipomas are often asymptomatic, soft and well displaceable. They can be palpated as soft and bulging lumps just under the skin. In some cases, pressing the lipoma may cause pain.

Fibromas are characterized by soft or approximately dermal neoplasms under or in the skin. They are often pedunculated and occur in mechanically exposed areas of the body (e.g., neck, armpits, groin). Fibromas often first appear during puberty, and overweight (obesity) promotes the development of fibromas.

Atheromas are always located near sebaceous glands (such as in the neck or armpits) and are pasty in consistency. Atheromas are bulging, elastic, visible elevations of the skin. A non-inflamed atheroma is usually painless. However, it can become a cosmetic problem depending on the body site and size. When inflamed, the affected skin around the atheroma reddens, swells and hurts with even light pressure.

Neuromas can cause pain that resembles a circumscribed pressure sore.

Diagnosis

A soft tissue tumor can often be recognized at first glance. However, a definite diagnosis can only be made after surgical removal of the tumor and subsequent fine-tissue (histological) examination. It is often not necessary for special diagnostics (such as a biopsy) to be performed before surgery.

At the beginning, the treating physician palpates the affected area under the skin and pays attention to whether it can be moved. To distinguish a lipoma from a fibroma or other soft tissue tumor, an ultrasound examination (sonography) is often used. Furthermore, soft tissue tumors can also be easily visualized by magnetic resonance imaging (MRI). If there is still doubt about the origin of the tumor after an imaging examination, a tissue sample can be taken and examined.

A typical fibroma is examined more closely for size, shape, color, texture and changes using a dermatoscope, a magnifying instrument. If a malignant neoplasm is suspected, tissue is often analyzed using a biopsy.

It is advisable to have all soft tissue tumors that cause discomfort or that show a progression in size examined or removed.

Hautnaht nach Entfernung eines Weichteiltumors (iStock / Akintevs)

Therapie

Therapy is usually performed by means of surgical removal of the tumor under local anesthesia. Sometimes, especially in unfavorable locations, general anesthesia is also necessary for removal. Since the extent of the tumor is small and assessable in most cases, a small incision is often sufficient for removal. Removal of surrounding tissue is not necessary for benign soft tissue tumors. Tumors that are stable in size and inactive may also be observed. Resection is recommended if there is pain or if the genesis of the tumor is unclear.

Special further treatment is not necessary in most cases, as the skin can be closed by suturing.

After removal, a soft tissue tumor should be examined histologically to ensure that it is not a malignant neoplasm.

Forecast

In most cases, soft tissue tumors can be removed without complications. Only very rarely do bleeding, infections, vascular or nerve injuries, and wound healing problems occur during removal. Complications can occur, for example, if tumors are particularly large or located in complicated areas (for example, near important nerves or vessels).

The prognosis for soft tissue tumors is very good. Lipomas or neuromas can sometimes form again after removal.

Sources

Dr. med. univ. Moritz Wieser

Dr. med. univ. Moritz Wieser

Thomas Hofko

Thomas Hofko

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