Clear cell sarcoma is a rare soft tissue cancer that most often develops in tendons of the arms or legs of young adults. Under the microscope, it has some features of malignant melanoma, a type of skin cancer, hence the reference of malignant melanoma of soft parts. It is an aggressive cancer that has a propensity for lymph node metastases.

This cancer develops as a tumor sticking out of the skin, most commonly on the back or abdomen. Dermatofibrosarcoma protuberans is uncommon, but occurs slightly more frequently in males than females. It can occur at any age, but is more likely to occur in adults. In its early stages, the tumor remains under the skin, and the skin surface will appear dark red-violet. If untreated, the tumor can break through the skin and form an open wound. The cancer has a tendency to recur, but rarely metastasizes. Treatment consists of surgical excision. If DFSP metastasizes, the use of a tyrosine kinase inhibitor such as imatinib can be effective at helping to control the tumor.

Desmoplastic small round cell tumors are a soft tissue sarcoma that typically begins in the abdomen. These tumors occur most often in young men and boys, though they can occur at any age and can also affect females. Desmoplastic small round cell tumors often form as multiple tumors in the tissue (peritoneum) that lines the inside of the abdomen and pelvis and can quickly spread to other structures within the abdomen. Treatment for desmoplastic small round cell tumors typically involves a combination of surgery, chemotherapy and radiation therapy.

Epithelioid sarcoma typically occurs in the hands or feet of young adults. It appears in the form of small nodules, which sometimes merge together. This sarcoma spreads to lymph nodes in approximately 20% of patients. Because of the nodules’ proximity to the joints, surgical excision can be difficult.

There are three types of extraosseous tumors, which are actually bone sarcomas found in the soft tissue: (1) mesenchymal chondrosarcoma; (2) extraskeletal osteosarcoma; and (3) Ewing's sarcoma (see pages 16-19). Chondrosarcomas and osteosarcomas may not be treated in exactly the same way as their bone varieties, but extraosseous Ewing's sarcomas are treated similarly and respond well to radiation therapy.

Fibrosarcomas usually occur in the arms, legs, or trunk, but can occur in any of the soft tissues. They can occur around scars, muscles, nerves, tendons, and the lining of bones. Fibrosarcomas typically invade local tissues and can spread through the bloodstream to the lungs.

Gastrointestinal stromal tumor (GIST) is a very rare cancer affecting the digestive tract or nearby structures within the abdomen. GIST most commonly affects older people, usually over the age of 50 years. Children are affected very rarely, and their disease is different than that in adults.

GISTs arise either from cells called interstitial cells of Cajal (ICCs) or from less differentiated stem cells or precursor cells that can develop into ICCs. The ICCs are known as the “pacemaker cells of the gut” because they send signals to trigger peristalsis, the digestive tract’s muscular contractions that move food along its course. Primary tumors are in the original site of development, before any spread to other locations. Primary GISTs may occur anywhere along the gastrointestinal tract from the esophagus to the anus. The most frequent site for GISTs is the stomach (about 55%), followed by the duodenum and small intestine (about 30%), esophagus (about 5%), rectum (about 5%), colon (about 2%), and rare other locations.

In GIST, the most common sites for metastasis are the liver and the abdominal membranes. Systemic treatment options include the use of tyrosine kinase inhibitors: imatinib, sunitinib, and regorafenib, as well as others.

Note: Information on GIST, above, was provided by GIST Support International.

Leiomyosarcomas are cancerous tumors that originate in the smooth muscle tissue. Smooth muscle is muscle over which the brain does not have conscious control, such as muscle in the walls of blood vessels, the uterus, or the gastrointestinal tract. These cancers can originate anywhere in the body, but the uterus or gastrointestinal tracts are the most common sites of origination, with over 60% of the GI tract tumors originating in the stomach. Uterine and GI leiomyosarcomas typically are accompanied by significant bleeding and pain. Metastases usually occur in the lungs or, in the case of GI tumors, in the liver. The average age of patients diagnosed with this type of sarcoma is 60 years. Leiomyosarcomas of the retroperitoneum and the vena cava are found mostly in women. The growth of tumors can accelerate during pregnancy. Treatment for uterine leiomyosarcoma is total abdominal hysterectomy.

You can read more information on Leiomyosarcoma. A new chemotherapy option for Leiomyosarcoma was approved in October of 2015. 

Liposarcomas arise in fat tissue and are the most commonly diagnosed soft tissue cancers. While liposarcoma tumors can develop anywhere in the body, they most often originate in the lining in the back of the abdominal cavity. They also occur in the thigh, the groin, the gluteal area, and behind the knee. Liposarcomas rarely develop from a pre-existing lipoma (for example, a non-cancerous tumor). The liposarcoma tumors are usually firm and bumpy and invade surrounding tissue aggressively. In approximately 10% of patients, the liposarcoma will spread to the lymph nodes. Liposarcomas are most often found in adults between 30 and 60 years old and are slightly more common in men than in women. There are several types of liposarcoma: atypical lipomatous tumor, myxoid liposarcoma, pleomorphic liposarcoma and dedifferentiated liposarcoma.

Lymphangiosarcoma, or Stewart-Treves Syndrome, is a malignant tumor originating from the endothelial cells of lymphatic vessels. Most lymphangiosarcomas arise in a lymphedematous arm secondary to radical mastectomy, but they sometimes complicate idiopathic lymphedema. The lymphedema has usually been present for 6-10 years before malignant changes develop.

Most cases arise from lymphedema induced by a radical mastectomy in breast cancer patients, with an average onset of 5-15 years and an occurrence rate of less than 1%. The three main indications for the development of Stewart-Treves in a lymphedemous limb appear to be radiation, extensive fibrosis, and recurrent or chronic infection.

The sarcoma first appears as a bruised area or a purplish discoloration in an extremity. The appearance of multiple "purplish" lesions with given patient history should cause a suspicion of lymphangiosarcoma. It progresses to an ulcer with crusting and finally to an extensive necrosis involving the skin and subcutaneous tissue. There also is often development of satellite spots from the original location. It metastasizes widely and there is no effective therapy or cure. Generally the affected area is excised, which includes the amputation of a limb when affected.

MFH has become the most common malignant sarcoma of older adults (age 50-70). This category of tumors has been renamed Undifferentiated Pleomorphic Sarcoma (UPS) by the World Health Organization (WHO). However, an MFH diagnosis is still commonly used by pathologists. These sarcomas are twice as common in men as they are in women. They tend to occur in the soft tissue of the extremities and the retroperitoneum (the anatomical space behind the abdominal cavity). However, it has been identified in nearly every organ of the body. Signs and symptoms relate directly to the location in which it arises. It is a diagnosis of exclusion; the burden of proof is upon the pathologist, and usually a battery of immunohistochemical studies must be done to exclude other sarcomas, such as rhabdomyosarcoma and liposarcoma.

There are four variations of MFH: storiform pleomorphic, myxoid malignant fibrous histiocytoma, malignant giant cell tumor of soft parts, and inflammatory malignant fibrous histiocytoma. Storiform and myxoid types of MFH are typically fast growing and invasive tumors, while the malignant giant cell MFH and inflammatory MFH tend to be slower growing and less invasive.

The malignant peripheral nerve sheath tumor (MPNST, Malignant Schwannoma or Neurofibrosarcoma) is the malignant counterpart to benign soft tissue tumors such as neurofibromas and schwannomas. It accounts for 5-10% of soft tissue sarcomas. It is most common in the deep soft tissue, usually in close proximity to a nerve trunk. The most common sites include the sciatic nerve, brachial plexus, and sarcal plexus.

The most common symptom is pain, which usually prompts a biopsy. Most tumors are more than 5 cm in diameter. MPNST is seen among patients with Type 1 Neurofibromatosis, or von Recklinghausen's disease. It usually occurs in people 20-50 years old, but patients with neurofibromatosis develop tumors at an earlier age.

These tumors typically spread to the surrounding soft tissue to form a nodular tumor. Metastasis can occur through the bloodstream. Tumors can be painful, and sometimes nerve function is affected. Treatment is generally wide resection of the nerve. Radiation therapy and chemotherapy can also be used.

Mesenchymoma is a rare soft tissue sarcoma showing two or more distinct types of malignant mesenchymal differentiation. It is generally thought that malignant mesenchymomas are high-grade sarcomas with a poor prognosis. However, low-grade malignant mesenchymomas have been reported and have had a better prognosis. These tumors are frequently located in the trunk (for example, the chest wall and retroperitoneum) and lower extremities (usually on the thigh). Mesenchymomas mainly occurs in adults. These tumors are quite invasive, especially when they occur in the skeletal muscles. Treatment is wide excision, often combined with radiation and/or chemotherapy.

Cancerous tumors in the skeletal muscles are one of the most common types of soft tissue sarcoma found in children. Over 85% of rhabdomyosarcomas occur in infants, children, and teenagers. Although most of our skeletal muscles are in our limbs and trunk, these cancers are most often found elsewhere in the body. The most common site is in the head and neck (30-40%) where it can grow near the eye, inside the mouth, or even near the spine in the neck. The next most common sites are the urinary and reproductive organs (20-25%) where it can start in the bladder, prostate gland, or any of the female organs. The least common sites are the arms and legs (18-20%), and trunk (7%). But these cancers can occur anywhere in the body, and not necessarily in a site that normally contains skeletal muscle. There are several different types of rhabdomyosarcoma:

Embryonal Rhabdomyosarcoma

The most common type, embryonal rhabdomyosarcoma (ERMS), tends to occur in the head and neck area, bladder, vagina, and in or around the prostate and testes. These usually affect infants and young children under the age of 10. Cells of embryonal (embryo-like) rhabdomyosarcomas resemble the developing muscle cells of a six- to eight-week-old fetus. Two variants of ERMS, botryoid and spindle cell, tend to have a better prognosis or outlook. Chemotherapy is very commonly used in treating these tumors, and there is a high cure rate when combination therapy (i.e. surgery and chemotherapy) is used. When there is a tumor seen at the surgical margin, radiotherapy is often added. Botryoid Rhabdomyosarcoma Botryoid rhabdomyosarcoma lesions usually occur in the genital region or urinary tract where they appear as a swollen lumpy mass. This form of sarcoma typically affects children under the age of seven.

Alveolar Rhabdomyosarcoma

The second main type, alveolar rhabdomyosarcoma (ARMS), occurs more often in large muscles of the trunk, arms, and legs, and typically affects older children or teenagers. This type is called alveolar because the malignant cells form little hollow spaces, or alveoli. This tumor is extremely aggressive and metastasizes widely at an early stage.

Pleomorphic Rhabdomyosarcoma

This type of sarcoma is usually found deep in the limb. Tumors can arise at many sites within the same muscle group and may grow very rapidly. The tumors generally spread through the bloodstream, although they can also spread through the lymphatic system. Unfortunately, this sarcoma has usually spread by the time of diagnosis. Treatment generally consists of surgery and chemotherapy. Pleomorphic rhabdomyosarcoma occurs in people over age 30 and commonly, but not exclusively, affects males on their extremities.

Primary synovial sarcomas are most common in the soft tissue near the large joints of the arm and leg but have been documented in most human tissues and organs, including the brain, prostate and heart. The most common site is adjacent to the knee, although they are also often found near the foot, ankle or hand. These sarcomas usually occur in young adults.

While synovial cells normally line the joints of the body, the name of this particular form of sarcoma is probably a misnomer, as synovial sarcomas do not necessarily arise in a joint, and the cancer cells in synovial sarcoma are likely to be very different from normal joint cells. The term “synovial” was chosen due to the cancer cell’s similarity, under a microscopic, to the normal synovial cells lining joints; however, the actual cells from which the tumor develops are unknown and not necessarily synovial.

Synovial sarcoma occurs most commonly in the young, representing about 8% of all soft tissue sarcomas but about 15-20% of cases in adolescents and young adults. The peak of incidence is before the 30th birthday and males are affected more often than females (ratio around 1.2:1).

Symptoms

Synovial sarcoma usually presents with an otherwise asymptomatic swelling or mass, although general symptoms related to malignancies can be reported such as fatigue. Unlike other soft tissue sarcomas, synovial sarcomas are often painful from the outset.

Treatment

Treatment usually involves:
Surgery, to remove the tumor and a safety margin of healthy tissue. This is the mainstay of synovial sarcoma treatment and is curative in approximately 20-70% of patients,depending on the particular study being quoted.

Conventional chemotherapy, (for example, doxorubicin hydrochloride and ifosfamide), to reduce the number of remaining microscopic cancer cells. The benefit of chemotherapy in synovial sarcoma to overall survival remains unclear, although a recent study has shown that survival of patients with advanced, poorly differentiated disease marginally improves with doxorubicin/ifosfamide treatment.

Radiotherapy to reduce the chance of local recurrence. The benefit of radiotherapy in this disease is less clear than for chemotherapy.