Courtesy: CR Chandrasekhar, Consulant Orthopaedic Surgeon Liverpool
Alpesh Mistry, MSK Radiologist, Liverpool
Susha Varghese, Pathologist, Liverpool

 

Practical Guide to Diagnosing Soft Tissue Masses

Overview

• Purpose: Concise, practical guidance on identifying and diagnosing soft tissue masses for clinicians.
• Audience: General surgeons, orthopedic surgeons, radiologists, pathologists, and other clinicians who evaluate soft tissue lumps.
• Main themes: clinical assessment, imaging strategy, biopsy technique, pathology role, multidisciplinary care.

Definitions and Key Differences

• Tumor: an abnormal mass of tissue in which cells continue to grow or fail to die normally; commonly described by patients as a lump, bump, or swelling.
• Benign tumor: usually localized, often encapsulated, slow growing, and unlikely to invade neighboring tissues or metastasize.
• Malignant tumor: has the capacity to invade locally and to spread to distant sites; metastasis is the defining feature of malignancy.
• Soft tissue sarcoma: a malignant tumor arising from connective tissue, uncommon, and often diagnosed at a larger size than common epithelial cancers.

Clinical Assessment

• History: obtain a clear timeline for the lump, associated symptoms (pain, growth), prior trauma, anticoagulant use, and relevant past or family medical history.
• Examination: inspect, palpate and assess mobility, consistency, tenderness, relation to skin, and whether the lump is superficial or deep relative to the deep fascia.
• Formulate a working diagnosis (benign, malignant, or indeterminate) based on history and examination before ordering investigations.
• Treat the patient, not just the lesion: consider comorbidities, social circumstances, and whether local resources can safely manage the case; refer when appropriate.

Common Benign Lesions

• Lipoma: common, soft, lobulated, mobile, usually non-tender; may occur in many locations.
• Ganglion cyst: typical around the wrist, hand, or foot; cystic and often compressible.
• Bursa enlargement (bursitis): frequently at predictable locations such as prepatellar and olecranon bursa.
• Epidermal inclusion cyst: contains keratinous debris and may be tethered to the skin.
• Vascular malformations and hemangiomas, fibromas, schwannomas and chronic hematoma (especially in patients on anticoagulants).
• Infective or inflammatory masses can mimic tumors and often improve with appropriate treatment.

Red Flags Suggesting Possible Sarcoma

• Size greater than 5 cm.
• Increasing size or rapid growth.
• Deep to the deep fascia (subfascial).
• New, unexplained lump without a convincing benign explanation.
• Recurrent lump after prior excision.
• Painful lump (though some sarcomas may be painless).

Imaging Strategy

• Use imaging to characterize the lesion, guide management, and plan biopsy or surgery.
• Ultrasound: first-line triage for many superficial lumps; operator dependent, rapid, low-cost, and provides dynamic assessment and vascularity via Doppler.
• Magnetic resonance imaging: used for indeterminate or suspicious lesions, lesions deep to fascia, or when local staging and surgical planning are required; typical protocol includes T1-weighted and fluid-sensitive sequences with fat suppression and axial planes.
• Computed tomography: reserved for limited indications, such as evaluation of mineralization, bone involvement, or when magnetic resonance imaging is contraindicated.
• Radiographs (plain X-rays): helpful when calcification or bony change is suspected.
• Imaging limitations: benign and malignant lesions can overlap in appearance; correlate with clinical information.

Role of the Radiologist and Biopsy Guidance

• Radiologists help triage lesions (benign, indeterminate, or suspicious) and select the most appropriate imaging modality.
• Ultrasound is frequently used to guide percutaneous core needle biopsy for accessible lesions.
• Computed tomography guidance is used for deep, retroperitoneal, or anatomically difficult targets where ultrasound visualization is inadequate.
• Magnetic resonance imaging guided biopsy is possible but requires specialized setup and is less commonly used because of logistical complexity.
• Biopsy planning must be coordinated with the surgeon to ensure the biopsy tract lies within the eventual surgical field to avoid contaminating otherwise uninvolved compartments.

Biopsy Technique and Diagnostic Yield

• Image-guided percutaneous core needle biopsy is the preferred initial approach when imaging or clinical features are not convincingly benign.
• Core needle biopsy typically aims to obtain 3–5 cores with 14 gauge preferred when feasible; smaller gauge needles may be used for very firm lesions.
• Diagnostic accuracy of image-guided core needle biopsy is high when representative tissue is obtained; sampling error occurs with necrotic or heterogeneous tumors.
• Small, superficial lesions less than about 3 cm may be suitable for primary excision instead of core biopsy if complete excision with clear margins is achievable and appropriate.
• Discuss anticoagulation management prior to biopsy and weigh bleeding risks against risks of stopping therapy; consider bridging strategies when necessary.

Pathology Role

• Pathologists examine hematoxylin and eosin stained sections and use additional tests to refine or confirm a diagnosis.
• Immunohistochemistry helps determine lineage and narrow differential diagnoses; select panels should be driven by morphology and clinical imaging.
• Molecular tests, including fluorescence in situ hybridization, reverse transcriptase polymerase chain reaction, or next generation sequencing, can confirm characteristic fusion genes or translocations in certain sarcoma subtypes.
• Core biopsy reports may provide subtype and an initial grade, but grading may be revised after resection, when more tumor is available for assessment.
• Report elements for resection specimens should include size, tumor subtype, grade, margin status, and provisional pathological stage.

Multidisciplinary Care Pathway

• Patients with suspected malignant soft tissue tumors should be managed by or discussed in a multidisciplinary team including surgeons, radiologists, pathologists and oncology specialists.
• Local diagnostic multidisciplinary discussion can guide initial imaging, biopsy approach and tissue handling.
• Regional sarcoma multidisciplinary meetings support final treatment planning for confirmed sarcoma, improving diagnostic accuracy and outcomes.
• Avoid unplanned excisions (‘whoops’ procedures) by performing appropriate imaging and biopsy prior to definitive surgery.

Anonymized Case Highlights

• Case A: A superficial foot mass that appeared cystic but proved to be a non-neoplastic infectious process after excision and special staining; illustrates that infections or granulomatous disease can mimic tumors.
• Case B: A rapidly enlarging thigh mass with extensive necrosis; initial core biopsy yielded necrotic material and a diagnostic sample was obtained from an involved lymph node, leading to diagnosis of an aggressive malignancy with characteristic marker loss and prompting timely resection.
• Case C: A mid-leg intramuscular lesion in a young adult; biopsy identified a myxoid liposarcoma subtype that responded to preoperative radiotherapy and required multidisciplinary management including chemotherapy for suspected pulmonary nodules.

Practical Recommendations for Clinicians

• Remember that most soft tissue lumps are benign, but do not assume any lump is benign without appropriate assessment.
• Urgent imaging (for example, ultrasound or magnetic resonance imaging) should be arranged for any unexplained or suspicious lump, following local guidance.
• Use ultrasound as a triage tool for many superficial lumps; proceed to magnetic resonance imaging for deep, large, or indeterminate masses.
• Plan biopsy with the multidisciplinary team so that the pathologist and surgeon are aware of targeting and future resection plans.
• Refer patients with suspected sarcoma to a regional sarcoma center or discuss in a regional multidisciplinary meeting where available.

Key Take-Home Points

• Obtain a careful history and perform a thorough examination for every soft tissue lump.
• Identify red flags early (size > 5 cm, deep location, rapid growth, recurrence, pain) and investigate promptly.
• Employ targeted imaging and image-guided core needle biopsy to maximize diagnostic yield while minimizing harm.
• Multidisciplinary collaboration between clinicians, radiologists, and pathologists is essential for accurate diagnosis and optimal treatment planning.