The arms, legs, pelvis, back of the human body are composed of bone, muscle and other tissues such as fat, fibrous tissue, blood vessels. Soft tissue sarcoma refers to a sarcoma that arises from the non-bony tissues of the extremity, pelvis or trunk. These tumors can arise directly from the muscles or from the other soft tissues between the muscles. They can also arise from the skin and subcutaneous tissues and fascia. The fascia is a thick sheet of tissue that underlies the skin and acts like an envelope around all the muscles of an extremity. It separates the skin and underlying fat from the muscles, blood vessels, nerves and bones of the extremities, pelvis and trunk.

Soft-tissue tumors are classified into various histological types. There are two reasons for classifying these tumors: the first is scientific in which tumors are classified based on their microscopic features. The second is for managerial purposes in which those aspects of the tumors are considered that bare solely on the clinical course of patients who are afflicted by them. Managerial classifications focus primarily on prognosis and treatment. Managerial classifications generally segregate tumors into benign, intermediate (borderline), and malignant-type soft-tissue tumors. This is actually a grading of the tumors that is determined by the pathologist based on the way the neoplasms look under a microscope. The grading correlates with their biological behavior. In other words, the grading of the tumor tends to correlate with the potential of the tumor to grow locally and to recur following resection and to spread to other body parts or to metastasize.

Generally, soft-tissue sarcomas are divided into the following broad classifications: fibrous and myofibroblastic tumors, fibrous histiocytomas, lipomatous or fatty tumors, smooth muscle tumors, skeletal muscle tumors, vascular tumors, perivascular tumors, synovial tumors, carilagenous and osteoid tumors, tumors of uncertain differentiation, and those in which differentiation is non-mesenchymal. Within each of these categories, tumors are further subdivided into benign, benign-aggressive, and malignant counterparts. Within the malignant category, they are further divided into low-grade, intermediate-grade, and high-grade tumors. Benign tumors tend neither to come back nor grow aggressively in an area in which they arise. Benign aggressive tumors tend to grow and invade the area in which they arise, however, they tend not to spread to distant body parts. Similarly, low-grade malignant tumors tend not to metastasize but rather grow invasively locally or to large sizes. The high-grade tumors, however, grow locally in a high-grade manner, tend to recur following resection, and tend to spread to distant body parts. High-grade tumors may metastasize to other body parts in 60%-80% of patients.

Click here for an Alternate Classification Scheme that Classifies Soft-Tissue Tumors according to Biological Behavior: Benign, Benign Aggressive and Malignant (Sarcomas)

Obviously, this scientific classification is very complex. It is difficult for patients to truly comprehend the intricacies of this classification system. In terms of clinical treatment, it is more important, however, to classify these tumors as benign, benign-aggressive (intermediate), or malignant.

Benign tumors are cured by a simple excision. The possibility exists that they may recur, however, they do not recur in a uncontrolled manner and they do not destroy normal tissue.

Intermediate tumors or benign-aggressive tumors can recur more commonly than purely benign tumors and are sometimes destructive, however, they never metastasize. Usually, wider margins are used to resect this type of tumor to prevent local recurrence. It is necessary to remove more normal surrounding tissue since these tumors tend to be more locally invasive. An example of this type of tumor is fibromatosis or extraabdominal desmoid tumor. Following resection, chemotherapy or radiation may be considered for these types of tumors to help control or eradicate microscopic disease. Chemotherapy may be given adjuvantly, although the use of adjuvant therapy such as chemotherapy and radiation therapy is much less common for the treatment of these tumors when compared to their malignant counterparts. Additionally, when chemotherapy is given, the assigned dosage is lower and the treatment is much less toxic.

Malignant tumors tend to recur locally when compared with benign or benign-aggressive tumors. Chemotherapy and/or radiation therapy, in addition to surgical resection, are usually considered in the treatment plan for these tumors. Surgical resection is considered the primary treatment modality and the best means for eradicating the primary tumor. Metastases to the lungs, other bones, and the liver occur commonly with these tumors.

Soft-tissue tumors or soft-tissue sarcomas most commonly arise from the deep muscles of the extremity. The thigh is the most common site, however, a soft-tissue sarcoma can really arise from any part of the body including any extremity including buttock, back, shoulder, arm, forearm, hands, feet, or calves. They can also arise from the subcutaneous tissues and the skin. They generally present as a painless mass that has increased in size over some time period. They may cause pain in some cases. Occasionally, a patient may give a history of a previous trauma or injury to the area that really has nothing to do with development of the soft-tissue tumor. Most likely, the injury draws the patient's attention to the tumor and the tumor then becomes more apparent. Sometimes a diagnosis of a hematoma is attributed to the lesion. Physicians and patients should be cautious when the diagnosis of a hematoma is rendered without a significant trauma occurring. Additionally, patients who are given the diagnosis of a lipoma based on the fact that they have a subcutaneous tumor, should be guarded, if this diagnosis was rendered purely on physical examination without an MRI. Most soft-tissue tumors will be biopsied unless they have a very characteristic benign appearance on a MRI. There are very few tumors that can be classified precisely by MRI. These include lipoma, hemangioma, and occasionally a schwannoma. Most other tumors should be biopsied. The biopsy method that I prefer is a core needle biopsy. A core needle biopsy, performed through a single stab incision in the skin and sampling of the tumor in multiple directions, will provide an experienced pathologist an adequate tumor sample to render an accurate diagnosis. This technique is just as accurate as an open biopsy. It is minimally invasive when compared to an open biopsy in which the patient requires surgery and where a skin incision is made. An open biopsy can result in a potentially tumor spreading hematoma and/or an infection. Occasionally, a core needle biopsy will be performed under CT-guidance in order to biopsy a specific region within a tumor, or for those tumors not palpable. Fine needle aspiration (FNA) is not recommended in the diagnosis of a soft-tissue tumor because it does not provide sufficient tissue to render an accurate pathological diagnosis.

It is important to emphasize that the ability for a high-grade soft-tissue tumor to metastasize does not depend solely upon its grading. Its size and location, if it arises deep within a muscle, deep to the fascia of an extremity, or whether it arises in a subcutaneous location also affects its ability to metastasize. Tumors that are greater than 5 centimeters in size, deep to the fascia of an extremity, and high-grade are the most likely tumors to metastasize. In addition to treating these tumors with surgical resection, radiation and chemotherapy are modalities often considered in the treatment of these tumors. It must be emphasized that soft-tissue sarcomas arise from the non-bony elements of the body. They arise from the muscles or fatty tissue or the intermuscular areas of the body. They are of mesenchymal cell origin, which is a fancy name for the types of cells that form the connective tissues in the body. Even though they grow from the soft tissues they do have the ability to grow into and destroy adjacent bones.