As with the benign bone tumors, there is no national registry of benign soft tissue tumors. By comparing Dr. Ward's 13 years of practice history from 1991 to 2004 and computing an incidence index relative to that of osteosarcoma, some estimate of the minimal prevalence of surgically treated lesions may be obtained.

From this index estimate, a baseline estimated extrapolation of the national incidence can be calculated. However, benign soft tissue tumors are the most likely category of tumors to be treated by other surgeons, such as general orthopedic surgeons, plastic surgeons, and general surgeons; therefore, this national estimate is extremely conservative. The prevalence and burden In the United States from benign soft tissue tumors is significantly higher than estimated herein. (Reference Table 6A.C.1 PDF CSV)

Benign soft tissue tumors are usually detected as asymptomatic masses. Treatment typically requires resection. Benign lesions rarely cause death, and it is rare that an amputation is necessary. However, depending on the site of involvement and size of the lesion, significant disability of the involved extremity and/or joint can occur. The true cost of these otherwise benign neoplasms can be high for healthcare costs, lost worktime, morbidity, emotional cost, and disability expenses.

Tumors of Fat Tissue

Lipomas: Benign tumors of fat tissue

Lipomas are the most common benign soft tissue tumor. Most are found under the skin, but they can develop anywhere in the body. Many lipomas are present for years and inactive, but those that are growing lesions are probably the most commonly resected soft tissue benign tumor. Resection of small growing lesions is usually performed in local community settings by multiple surgical specialists and even by primary care practitioners. Only patients with larger, more concerning lesions are typically referred to surgeons with a focus in surgical oncology. Not infrequently, a slow-growing sarcoma is mistakenly diagnosed as a lipoma, leading to a delay in the diagnosis of soft tissue sarcoma. This misdiagnosis can lead to an original suboptimal resection of the unappreciated sarcoma by the unsuspecting community surgeon.

Lipoblastomas

Lipoblastomas are benign fat tumors that occur in infants and young children.

Hibernomas

Hibernomas are benign fat tissue tumors that behave similarly to lipomas. They are so named because of their brownish coloration that resembles the appearance of the fatty tissue of bears, hence the name hibernomas. They are much less common than lipomas.

Tumors of Muscle Tissue

Leiomyomas (Smooth Muscle Benign Tumors)

Smooth muscle is found in internal organs such as stomach, intestines, blood vessels, or uterus. Unlike skeletal muscle that contracts voluntarily, smooth muscle contracts involuntarily. Leiomyomas are benign tumors of smooth, or involuntary muscle. Leiomyomas can arise almost anywhere in the body in either men or women because they start in widespread tissues such as blood vessels or intestine. The most common leiomyomas is the fibroid tumor that often develops in the uterus.

Rhabdomyomas (Skeletal Muscle Benign Tumors)

Skeletal muscle is the muscle that allows movement of arms and legs and other body parts. These are voluntary muscles. Rhabdomyomas are benign tumors of skeletal muscle and are very rare.

Benign Tumors of Peripheral Nerve Tissue (Benign Peripheral Nerve Sheath Tumors)

Neurofibromas, schwannomas (neurilemmomas), and neuromas are benign tumors of nerves. These tumors can occur almost anywhere in the body. An Inherited condition called neurofibromatosis, or Von Recklinghausen disease, causes people to develop many neurofibromas throughout their body. Some of these may dedifferentiate and become malignant. These dedifferentiated malignant tumors usually form from large neurofibromas in the upper arms, neck, pelvis, or thigh. Patients with the dedifferentiated neural sarcomas have a very poor prognosis and most ultimately succumb to the cancer.

Tumors of Joint Tissue

Joints are surrounded by tough tissue called synovium, which produces fluid that lubricates joint surfaces allowing them to move smoothly. Joint tissue tumors typically arise from the synovium.

Pigmented villonodular synovitis (PVNS) is a benign tumor of joint tissue. It is most common in its nodular form in the hands, and more common in women than in men. The nodular form rarely recurs following adequate and complete excision. PVNS also occurs in a diffuse form that typically will involve the entire joint lining and has a high recurrence rate after attempted resections. PVNS in its diffuse form is most commonly encountered in the knee joint, where it often causes recurrent bloody effusions (swollen knees filled with bloody fluid). It does not spread to other joints, but when recurrent or persistent, can destroy the involved joint.

Tumors of Blood Vessels and Lymph Vessels

Hemangiomas are benign tumors of blood vessels. They are rather common, are often present at birth, and can affect the skin or internal organs. They sometimes disappear without treatment, but when located in muscles and other deep tissues, can be quite problematic and may require surgical treatment.

Glomus tumors are benign perivascular (surrounding blood vessels) tumors. They usually are found under the skin and often under fingernails. They are usually small (<1 cm), but are exquisitely tender and painful. They may make the overlying skin sensitive to even light touch from clothing.

Hemangiopericytoma is a tumor of perivascular tissue. It most often develops in the legs, pelvis, and retroperitoneum (the back of the abdominal cavity) and is most common in adults. These can be either benign or malignant. They rarely spread to distant sites but tend to recur locally following surgical resection unless very widely excised. They may be multifocal.

Lymphangiomas are benign lymph vessel tumors that are usually present at birth. Lymph is a type of fluid that circulates in every tissue of the body. Lymph fluid is collected and routed back into the venous system by the lymphatic system. It contains waste products from tissues and immune system cells. Lymphangiosarcomas are the malignant lymph vessel equivalents of angiosarcomas.

Tumors of Fibrous Tissue

Fibrous tissue forms tendons and ligaments and covers bones as well as other organs in the body.

Fibromas, elastofibromas, extra-abdominal fibromatosis, and fibrous histiocytomas are all benign soft tissue tumors. Fibromatosis is the most problematic of these tumors. They frequently recur following resection, and may require additional treatment with repeat surgery, radiation therapy, chemotherapy, or other therapies. Although these tumors do not metastasize, they can be challenging. Fibromatoses (desmoid tumors) were discussed at length under the malignant soft tissue section above where they are often grouped due to their locally aggressive nature.

Tumors of Uncertain Tissue Type

Through microscopic examination and other laboratory tests, doctors can usually find similarities between most soft tissue tumors and certain types of normal soft tissues. This is how soft tissue tumors are classified. However, some soft tissue tumors have not been linked to a specific type of normal soft tissue.

Myxoma is a benign tumor that is usually located in muscles but does not develop from muscle cells. The cells of a myxoma produce mucus-like material in and around the cells, a distinguishing feature of this tumor. They are usually found in adults, and rarely recur after treatment. Myxoma must be differentiated from myxofibrosarcoma, a malignant neoplasm that can appear very similar under the microscope as well as in gross appearance. The challenge for the treating physician is to avoid overtreating myxomas and to avoid undertreating myxofibrosarcomas, in terms of the extent of normal tissue margin around the tumor to be resected with the tumor to minimize the risk of recurrence.

Granular cell tumors are very uncommon and are usually benign tumors of adults that can be found almost anywhere in the body. They are frequently multifocal.

Tumor-like Conditions of Soft Tissue

Some conditions of soft tissues are caused by inflammation or injury that forms a mass similar to a soft tissue tumor. Unlike a true tumor, they do not come from a single abnormal cell; they have limited capacity to grow or spread to nearby tissues, and never spread through the bloodstream or lymph system. Examples include nodular fasciitis and myositis ossificans, which involve tissues under the skin and muscle tissues, respectively.

There are also deposition diseases that are often grouped with tumors. The most commonly encountered ones are tophi, often seen in cases of poorly controlled gout. These tophi can achieve massive size and may be mistaken for true tumors. They can erode through the skin, causing skin breakdown and infection that may require surgical treatment and antibiotics. Calcium deposits are often seen in renal failure and poorly managed dialysis patients. They may be painful and may require difficult resection of deposits infiltrated into normal tissue. When not associated with diseases of abnormal calcium metabolism, such as renal failure and dialysis, the disease is termed tumoral calcinosis. It behaves essentially the same as the calcium deposition mentioned in association with renal disease. Amyloid deposition can rarely cause a soft tissue (or bony) mass. These are most often seen in poorly controlled dialysis patients. Rheumatoid nodules are soft tissue deposits of antibody-laden, inflammatory soft tissue masses that can be quite painful and may require resection for symptomatic relief. Adequate treatment of the underlying rheumatoid arthritis with current disease-modifying medications usually prevents the occurrence of such lesions.