In this article, we will talk about the most important neoplastic diseases of the soft tissues including tumors of the lipid tissue, fibroblast, muscle tissue, synovial cell sarcoma, and dystrophin diseases. Moreover, we will also cover the topics of primary and specific amyloidosis.

Lipoma

Image : “Lipoma 02” by Sikander Iqbal. License: CC BY-SA 3.0


Overview

Dystrophin associates with different proteins in skeletal and cardiac muscle to form what is known as dystrophin-associated protein complex (DAPC). This structural protein is needed for the optimum functioning of actin and is known to stabilize the sarcolemma of the muscle cells. If lost or became dysfunctional, the muscle cells fail to contract and relax, and Duchenne muscular dystrophy develops.

The etiology of muscular dystrophy is established by an abnormality in the genetic code for specific translation of muscle proteins.They are generally classified in relation to their clinical phenotype, the pathology, and mode of genetic inheritance. This inheritance includes several patterns like the sex-linked, autosomal recessive, and autosomal dominant muscular dystrophy. Several disorders characterized by their clinical presentation and pathology do exist in these groups.

Heritable muscular dystrophy include the following:

  • Autosomal dominant muscular dystrophy for example. Facioscapulohumeral, distal, ocular, oculopharyngeal.
  • Sex-linked muscular dystrophy for example Duchenne, Becker, Emery-Dreifuss
  • Autosomal recessive muscular dystrophy for example,  Limb-girdle form

An adipose tissue neoplasm is a tumor derived from lipid or adipose tissue. The most common example is a lipoma which we will discuss in this article.

The cause of lipomas is largely unknown. However, scientist have described an association between lipomas and gene rearrangements of chromosome 12 more so with solitary lipomas.

Lipoma is thought to be related to traumatic events due to several theories such as:

  • Upon traumatic events fat ay herniate through spaces in tissue planes created by the traumatic forces.
  • Cytokines released during trauma may trigger pre-adipocyte differentiation and maturation.

Tumors that derive from the fibrous tissue are known as fibrous tissue neoplasms.

Tumor Derives from…
Fibroma Fibrous tissue
Myoma and myosarcoma Muscle tissue
Synovial cell sarcoma Synovial tissue

Organ-limited amyloidosis, also known as specific amyloidosis, is a form of amyloidosis that affects primarily a single organ. Organ-limited amyloidosis can be classified into neurological amyloid and cardiovascular amyloid disease. Primary systemic amyloidosis involves multiple organs.

Epidemiology of Soft Tissue Pathologies

Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is a genetic disorder that is characterized by progressive muscle weakness due to muscle degeneration. It is characterized by the absence of dystrophin. The estimated prevalence of DMD in males aged between 5 and 24 years is 1 in every 7250 individuals. DMD is least common in the African American population.

Lipoma as an Example of Adipose Tissue Neoplasms

Lipoma is a benign tumor of the lipid tissue. Up to 2% of the general population are affected by lipomas. Lipomas are most commonly seen in adults aged between 40 and 60 years. The male to female ratio is 1:1. Lipomas are the most common noncancerous soft tissue tumor.

Fibroma as an Example of Fibrous Tissue Neoplasms

Fibroma is a benign tumor that derives from the fibrous tissue. Fibromas can grow n all organs and they derive from the fibroblastic cells. Fibromas are common in the general population.

Myoma and Myosarcoma as Examples of Muscle Tissue Neoplasms

Myomas can be classified into leiomyoma and rhabdomyomas. Leiomyomas are common in women and they present as uterine fibroids. Rhabdomyomas are rare tumors of muscle tissue that arise in children and can become malignant.

Myosarcoma can be also classified into leiomyosarcoma and rhabdomyosarcoma depending on whether they arise from smooth muscle or striated muscle. These malignant tumors are rare.

Synovial Cell Sarcoma

A synovial sarcoma is a rare form of cancer that occurs in the arms and legs in close proximity to joint capsules and tendon sheaths. They arise from synovial cells. The estimated incidence of synovial cell sarcoma is around 2 per 100,000 per year. They occur most commonly in the third decade of life and are found more often in males.

Organ-Limited versus Primary Systemic Amyloidosis

The incidence and prevalence of primary systemic amyloidosis in the United States are unknown. Recent epidemiological studies estimated the incidence of primary systemic amyloidosis to be around 5.1 to 12.8 per million per year. Approximately, 3000 new cases of primary systemic amyloidosis occur in the United States each year. The mean age of onset is 65 years. The prognosis is poor, and most patients develop cardiac and renal failure.

Organ-specific amyloidosis includes many diseases such as:

Accordingly, to give an estimate of an incidence of organ-specific amyloidosis is not possible.

Clinical Presentation of Soft Tissue Pathologies

Duchenne Muscular Dystrophy

The symptoms of DMD occur by the age of 3 years. The first muscles to be affected are the proximal ones (hips, pelvic area, thighs, and shoulders). The muscles of the arms, legs, and trunk are affected when the disease progresses. The calves become enlarged. Heart and respiratory muscles are also affected in DMD because dystrophin protein is also found in these muscles.

Lipoma

The main risk factors for lipoma include:

  • Family history
  • Obesity
  • Sedentary lifestyle

The diagnosis of a lipoma is usually a clinical one that is supported by imaging findings. Ultrasound is useful in assessing a deep lipoma such as a breast lipoma. Magnetic resonance imaging is useful in the assessment of lipomas that occur in the extremities.

Fibroma

A hard fibroma consists of many fibers and few cells. A keloid which develops after a scar undergoes hyperplastic growth is a type of hard fibroma. Soft fibromas present as skin tags. They appear on the neck, armpits, and groin. They can be also found on the eyelid.

Myoma and Myosarcoma

These tumors present as lumps that are found deep in an extremity. Uterine fibroids present with symptoms and signs suggestive of a fibroid such as lower abdominal distension, constipation, and painful intercourse. Malignant muscle tissue tumors typically occur in children.

Synovial Cell Sarcoma

Synovial sarcomas present as asymptomatic swelling or mass near a joint capsule or a tendon. They can also present with constitutional symptoms such as fatigue. The diagnosis is confirmed by histology where the chromosomal translocation t(X;18) is found. Defects appearing inthis chromosomal translocation is directly associated with the underlying cause of the tumor. This specific chromosomal translocation between chromosome X and chromosome 18 has been mainly observed in most cases.

The tumor has a high risk of metastasis that is influenced by tumor size, anatomic location and tumor grade.

Organ-Limited versus Primary Systemic Amyloidosis

The symptoms and signs of organ-limited amyloidosis depend on the organ involved. For instance, in the case of Parkinson’s disease, the patient develops symptoms and signs suggestive of Parkinson’s disease.

The most common symptoms would be:

  • Tremor
  • Dyskinesis
  • Gait disturbances

The presenting symptoms of primary systemic amyloidosis include fatigue, weight loss, paresthesia, hoarseness and edema. Patients might also develop carpal tunnel syndrome, the tongue might become enlarged, and they might develop hepatomegaly. Patients with cardiac and/or heart involvement can present with heart or renal failure.

Petechiae and ecchymoses occur in up to 40% of the cases of primary systemic amyloidosis. They give you the first clue about the diagnosis.

Patients with primary systemic amyloidosis typically have proteinuria, elevated serum creatinine levels, and elevated liver enzymes. Echocardiography is indicated for the evaluation of the heart. A thickened left ventricle is a common finding when the heart is involved.

Treatment of Soft Tissue Pathologies

Duchenne Muscular Dystrophy

The treatments of DMD include braces, standing frames, and wheelchairs. Because the heart is commonly involved, a complete cardiac evaluation is recommended in early childhood. The cardiac evaluation needs to be repeated every other year until the age of 10 years. After that, cardiac evaluations are to be done each year. Steroids might be effective in slowing the progression of DMD.

Lipoma

Lipomas usually do not require any treatment. If the tumor becomes painful or restricts movement, it can be removed. A simple excision procedure is all that is needed.

Common complications include:

  • Recurrence of the tumor if full surgical excision with the capsule is not achieved.
  • Nerve injury.
  • Cosmetic blemish.
  • Nonsurgical therapy comprises endoscopic excision of tumors located in hollow organs of the abdomen.

Fibroma

Benign fibromas do not need any treatment. If removal is needed, it can be done in a brief outpatient procedure.

Myoma and Myosarcoma

These rare tumors are usually malignant. They require chemotherapy, radiotherapy, and excision. They have a poor prognosis.

Synovial Cell Sarcoma

The tumor needs to be removed by a safe margin. This is usually curative in up to 70% of the cases. Chemotherapy with doxorubicin hydrochloride and ifosfamide might be needed to reduce the remaining microscopic metastases. Radiotherapy can be helpful in preventing local recurrence.

Treatment of Primary Systemic Amyloidosis

Chemotherapy with vincristine, doxorubicin, and dexamethasone followed by high-dose melphalan and then autologous peripheral blood stem cell transplantation can be used to treat primary systemic amyloidosis. Despite the availability of this experimental regimen, the prognosis of primary systemic amyloidosis remains to be poor.

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