A muscle is defined as tissue composed of cells or fibers that effect movement of an organ or part of the body via contraction. A neoplasm is the formation of new and abnormal tissue, such as a tumor or growth. A benign neoplasm, or growth does not spread by metastasis or infiltration of tissue. Benign soft tissue tumors may originate from fibrous, fatty, muscle, vascular, or nerve tissue. In this case, it occurs in the muscle.

Muscle tumors are rare, and are usually benign. Predisposing factors associated or linked to benign tumors include a family history of benign tumors; environmental factors including viruses; environmental exposure to chemicals, drugs, alcohol, and tobacco; and prior illnesses, such as an autoimmune disease, previous immunosuppressive therapy, and acquired immunodeficiency syndrome (AIDS).

Signs and symptoms may manifest as a lump in a muscle that may be felt on the surface of the skin. There may or may not be pain. The size of the lump may rapidly increase or grow to a certain size and stop. There may be change in muscle function or sensation. Extensive bleeding within a lesion may occur. With lumbosacral tumors, there may be neurologic deficits. Swelling, redness, or restricted range of motion may occur.

X-ray; magnetic resonance imaging (MRI); computed tomography (CT) scan; ultrasonography; blood studies; and tissue biopsy may be required.

Depending on the type of tumor, treatment may vary from no treatment to surgical resection or excision. Amputation may be necessary for rare forms of lipomas. In some cases, radiation therapy may be indicated. Mild to moderate pain may be treated with analgesics and nonsteroidal anti-inflammatory drugs (NSAIDS).

The rate of recurrence of tumors may vary depending on the specific tumor type. A few benign tumors may become malignant. Residual effects may depend on the tumor location, extent of surgery and need for radiation therapy. There may be neurologic deficit, muscle weakness, muscle contractures, joint deformity, or decreased range of motion. Long-term follow-up and rehabilitation may be necessary.

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