Benign soft tissue tumors are categorized according to their behavior.

Benign Soft Tissue Tumors Soft tissue tumors develop in connective tissue other than bone such as the skeletal muscle, fat, tendon, fibrous tissue and nerve and blood vessel (neurovascular) tissue.

Soft tissue tumors can occur anywhere in the body but are most frequent in the lower extremities, trunk and abdomen and upper extremities. The cause is unknown. Trauma may bring attention to a previous existing tumor.

Benign soft tissue tumors rarely metastasize. They are categorized according to their behavior to be aggressive or not, ranging from inactive, to active, to aggressive.

In adults, the most common benign soft tissue tumor is a lipoma. In children, popliteal (Baker's) cysts, lipomas and hemangiomas are common. Benign tumors may be very large and deep but are usually soft - except for the fibrous tumors which may feel firm.

Lipoma The most common benign soft tissue tumor made of fat and is usually large and soft. They are located on the back, shoulders, abdomen and upper and lower extremities. They usually do not cause symptoms unless they begin to push on nearby nerves. Lipomas usually grow slowly with little change over many years. Many patients seek medical attention for cosmetic reasons when a lipoma grows too large. An angiolipoma which involves blood vessels usually occurs in children located deep in the muscle and is tender because it involves the vessels. On the MRI scan, the lipoma is seen as a bright, well defined mass. Treatment includes removing (excising) the mass or observing it if it is not bothersome. Recurrences are unusual.

Hemangioma A benign vascular (involving blood vessels) soft tissue tumor. It is the most common soft tissue tumor in children. It can develop in the top skin (superficial) layer or deep within the muscle. They occur more often in the lower extremities than the upper extremities. Hemangiomas can range from being well-defined, noninvasive and involving small vessels (capillaries) to less defined, invasive and involving large vessels. The most common type of hemangioma is made of both large and small vessels. The MRI scan is the best type of imaging to show the location and extent of the tumor. Angiograms may also be done to evaluate the large blood vessels.

Treatment is not necessary unless they cause pain. Aspirin and compression stockings may be quite successful in relieving symptoms. Surgical excision is sometimes necessary if symptoms persist. Although hemangiomas are vascular, they do not spread to other areas or turn malignant. Occasionally for large tumors that can not be removed, radiation therapy and embolization (a procedure to plug/stop the blood supply in the tumor area preventing tumor growth) has been attempted to treat hemangiomas with little success. Recently, treatment has also included injections with alcohol into the tumor (sclerotherapy).

Fibroma and Fibromatosis Benign soft tissue tumors made of fibrous tissue come in many different forms. Congenital fibromatosis occurs in infants and usually presents as a solitary mass. Fibrous tumors in adolescents and adults include fibromas, extra-abdominal desmoid tumors, palmer fibromatosis and nodular fasciitis. Fibromatosis (desmoid tumor) refers to a benign but aggressive tumor usually located in the lower extremity. Fibromatoses are very aggressive at the original site and invade the nearby muscle, soft tissue and bone but do not metastasize (spread to other sites). MRI scans or CT scans are done preoperatively. Plain x-rays will rule out any bone involvement under the soft tissue mass, and a bone scan will show any other bony invasion.

Treatment includes removal (excision) of the soft tissue mass. In some cases the surgical margin (area around the tumor) is not large enough because the tumor extends microscopically beyond the main mass. Thus, there is a high rate of recurrence. These tumors should be treated aggressively with wide margin excisions. Radiation therapy is also used for local control.

Neurofibroma and Neurofibromatosis Benign soft tissue tumors that are made of nerve tissue. They are also called nerve sheath tumors or schwannomas because the tumor tissue has cells like the nerve sheath (envelope around the nerve fibers), or Schwann cell. Neurofibromas may occur as a single tumor or many tumors and may be found anywhere on the body. They range from simple, small masses to gross enlargement of an extremity (elephantiasis), to masses causing bony erosion and deformities of the spine. Since neurofibromas come from nerve roots, those located in the spine can press on the spinal cord causing neurologic symptoms.

Neurofibromatosis is an inherited syndrome and is the most common genetic disorder, usually diagnosed in childhood. The patient presents with greater than six cafe au lait spots ('coffee with milk' colored, brownish, birthmark spots on the skin) and/or many neurofibromas (called von Recklinghausen's disease) over their entire body. Patients with severe disease may have large neurofibromas involving an entire extremity.

An MRI scan is necessary to evaluate the size and extent of the neurofibroma. The mass is usually seen in connection with a major nerve. Examination of the tumor tissue shows a tumor composed of spindle cells. The treatment involves excision of neurofibromas if they are large, painful or interfere with function. Single neurofibromas once excised rarely recur. The multiple neurofibromas of neurofibromatosis may become malignant. Most often they are observed and not excised unless they are growing or painful. If a sarcoma develops, the patient must undergo staging studies to rule out metastatic disease. Pre- and/or post-operative radiation therapy is usually included in the treatment plan, and sometimes chemotherapy.

Pigmented Villonodular Synovitis (PVNS) A benign soft tissue mass involving the synovial membrane (lining of a joint). It is most often seen in the knee or hip joint of adults under age 40. Patients usually present with a boggy, swollen, painful joint. The synovial membrane becomes thick. Many times the disease process goes beyond the joint and causes severe degenerative joint disease. If an aspirate (fluid withdrawn from an area with a needle) of the joint is done, it will show a bloody, brown fluid. Other diagnoses that must be ruled out are infection, rheumatoid arthritis, hemangioma, giant cell tumors of tendon sheath or malignant synovial sarcoma. X-rays of PVNS show an increase in joint fluid, a thick synovial membrane and sometimes bone erosion. Bone scans show increased activity in the joint area, and synovial thickening and nodularity or a mass are seen on the MRI scan. A biopsy should be performed on large nodular tumors to rule out sarcoma. Tumor tissue reveals many rounded synovial-like cells with a good amount of giant cells and inflammatory cells. Treatment involves an excision of the tumor. If the PVNS is widespread, a complete synovectomy (excision of the membrane that lines joints lubricating them with fluid) must be done. Localized nodular synovitis is simply excised. PVNS may recur unless the entire synovial membrane is removed. Widespread PVNS usually causes chronic degenerative joint disease which may require total joint replacements. Radiation is an alternative adjuvant therapy in recurrent cases.

Myositis Ossificans A non-tumorus soft tissue mass that occurs after a blunt trauma. The soft tissue reacts to the trauma by forming a bony mass. Patients present with a painful or painless mass which is increasing in size. The tumor is usually located in the upper arm, thigh or buttock. X-rays show a round ossified (bony) mass which may be read as a sarcoma. However, the myositis ossificans has a distinct margin of ossification (bone formation) with an active center containing immature cells. Sarcomas have active and inactive tissues on the outer margin with an inactive center. Bone scans show increased activity in the area of the mass for about 8-12 weeks, and then the activity decreases. The CT scan is the best imaging to show the bony mass. Treatment involves observation or excision usually after an 8-12 week period because if it is excised before full maturation, recurrence is likely. There lesions sometimes resolve without treatment.

Ganglion or Synovial Cyst A benign soft tissue mass 'cyst like' in nature and comes from the capsule of the joint, synovial membrane (lining) or tendon sheath (covering). It usually develops on the top of the wrist in adults between 25 and 45 years of age, and are more common in women. The cause is unknown, but repeated trauma is a contributing factor. Some patients have no symptoms, while other have tenderness, pain and problems with wrist function. A needle aspiration should be done if a sarcoma is suspected. Staging studies are usually not necessary because of the ganglion cyst's classic appearance, although ultrasound is helpful in confirming the cystic nature of the lesion. The excised cyst or nodule has an outer fibrous layer with an inner lining made of clear colorless, gelatin-like fluid.

Some ganglia need no treatment because they go away on their own. Usually needle aspiration or rupture of the cyst give temporary relief. Recurrence is common. The best treatment for a patient who has symptoms is to completely excise the cyst down to the base of the cyst which should prevent recurrence. Baker's cysts behind the knee in children nearly always resolve without treatment.