Soft Tissue Abnormality / Mass
A soft tissue abnormality or mass refers to any unusual growth, lump, or area of abnormal tissue in the soft tissues of the body—including muscles, tendons, ligaments, fat, blood vessels, nerves, and connective tissues. These abnormalities can range from benign, harmless lumps like lipomas (fatty tumors) to more serious conditions including infections, inflammation, or malignant tumors. Soft tissue masses can occur anywhere in the body and vary greatly in size, symptoms, and clinical significance, making proper evaluation through imaging and sometimes biopsy essential for diagnosis.
What is it?
Soft tissues comprise all the non-bony, non-organ structures in the body, including muscles, fat, fibrous tissues, blood vessels, lymphatic vessels, nerves, and various types of connective tissue. A soft tissue abnormality or mass represents any deviation from normal architecture—whether an enlargement, unusual texture, abnormal growth, or inflammatory change. These abnormalities can be broadly categorized into benign tumors (non-cancerous growths that don’t spread), malignant tumors (soft tissue sarcomas and other cancers), pseudotumors (tumor-like conditions that aren’t true neoplasms, such as hematomas or cysts), and inflammatory or infectious processes.
Common benign soft tissue masses include lipomas (the most common, composed of mature fat cells), hemangiomas (collections of blood vessels), schwannomas and neurofibromas (nerve sheath tumors), fibromas (fibrous tissue growths), ganglion cysts (fluid-filled sacs near joints or tendons), and various other lesions. Soft tissue sarcomas are relatively rare malignant tumors that can arise from any soft tissue type, including liposarcoma (from fat), leiomyosarcoma (from smooth muscle), rhabdomyosarcoma (from skeletal muscle), synovial sarcoma, and undifferentiated pleomorphic sarcoma. Warning signs suggesting malignancy include rapid growth, size greater than 5 cm, deep location (beneath the fascia), firmness or fixation to underlying structures, and pain (though many benign masses can also be painful). However, imaging and biopsy are essential for definitive diagnosis as clinical examination alone cannot reliably distinguish benign from malignant lesions.
Important to Know
Most soft tissue masses present as a palpable lump or swelling that may or may not be painful. Additional symptoms depend on location and size—large masses may cause pressure symptoms, nerve compression leading to numbness or weakness, vascular compression affecting blood flow, or limitation of movement if near joints. Some masses are discovered incidentally during imaging for other reasons. Diagnosis begins with physical examination assessing size, location, mobility, consistency, and tenderness. MRI is the gold standard imaging modality for characterizing soft tissue masses, providing excellent detail of tissue composition, extent, and relationship to surrounding structures. Ultrasound is useful for superficial masses and can distinguish solid from cystic lesions. CT may be used for certain locations or to assess for calcifications. However, imaging features alone often cannot definitively distinguish benign from malignant tumors, particularly for borderline or atypical lesions. Biopsy (either needle biopsy or surgical excisional biopsy) with pathological examination is necessary for definitive diagnosis when there is concern for malignancy or when the diagnosis is uncertain. Treatment depends on the specific diagnosis—many small, benign, asymptomatic masses can be observed without intervention; symptomatic benign tumors may be surgically removed; soft tissue sarcomas typically require wide surgical excision, often combined with radiation therapy and sometimes chemotherapy. The prognosis varies dramatically based on whether the mass is benign or malignant, and for sarcomas, depends on tumor grade, size, depth, and whether it has spread to other sites. Early evaluation of concerning soft tissue masses allows for timely diagnosis and optimal treatment outcomes.