Soft tissue metastasis

Disease Description (Causes and Symptoms)

• Definition: Soft tissue metastasis refers to a condition in which cancer cells originating in another site (the primary cancer) travel through the bloodstream or lymphatic vessels and settle and proliferate in soft tissues other than bone or cartilage, such as muscle, fat, tendons, ligaments, and joint capsules.
• Pathophysiology: Cancer cells separated from the primary tumor spread through blood vessels or lymphatic vessels, adapt to the soft tissue microenvironment, induce new blood vessel formation and stromal changes, and form a tumor mass. Metastasis is determined by interactions between the molecular characteristics of the tumor (metastasis-related genes, surface receptors, etc.) and the host environment.
• Causes (major associated primary cancers): It may occur in various cancers, including breast cancer, lung cancer (small-cell and non-small-cell), colon and rectal cancer, stomach cancer, pancreatic cancer, liver cancer, renal cell carcinoma, thyroid cancer, and skin cancer (melanoma).
• Main symptoms: Symptoms vary depending on the metastatic site — localized mass (lump), swelling, pain, limited movement, and skin changes (redness and ulceration), among others. Systemic symptoms such as weight loss, fatigue, and fever may also occur.
• Diagnostic approach: A biopsy (needle biopsy or excisional biopsy) is performed to determine whether the lesion is malignant and to identify the histology of the primary cancer. Imaging tests such as CT, MRI, and FDG-PET, and, when necessary, blood tests and tumor marker tests are performed to assess the stage and extent of metastasis.

Treatment Methods (Including Standard Treatment, Medications, Procedures/Surgery, and Lifestyle Management) and Precautions

• Overall treatment after diagnosis: Treatment varies depending on the type, grade of differentiation, and molecular phenotype of the primary cancer; the number, size, and location of metastases; and the patient's overall condition (performance status and comorbidities). Multidisciplinary consultation (including medical oncology, surgical oncology, and radiation oncology) is recommended.
• Local treatment
  • Surgery: When the metastasis is localized and solitary, can be resected, and functional preservation is considered reasonable, complete resection is performed through wide excision (including surrounding normal tissue). Reconstruction and rehabilitation after resection should be considered.
  • Radiation therapy: Used to relieve symptoms of a local lesion (pain, bleeding, and nerve compression) or for local control. The dose and fractionation are determined according to the brachytherapy (radiation selection) approach.
• Systemic treatment
  • Chemotherapy: Standard chemotherapy for the primary cancer is applied (the drug combination varies depending on the primary tumor).
  • Targeted therapy/molecular targeted therapy: May be used when genetic mutations or target proteins of the primary cancer are identified (e.g., EGFR/ALK in lung cancer).
  • Immunotherapy: Immune checkpoint inhibitors may be used for cancer types with an indication.
  • Hormone therapy: Used in cases of hormone-dependent primary cancers (e.g., breast cancer).
• Symptom management and supportive treatment
  • Pain management (analgesics, nerve blocks, etc.), wound care (ulceration and bleeding), nutrition, rehabilitation, and psychosocial support.
  • Referral to palliative care or hospice when necessary.
• Precautions and risk of complications
  • Infection, bleeding, and functional impairment may occur after surgery; systemic adverse effects of radiation therapy and chemotherapy may occur (such as bone marrow suppression, nausea and vomiting, and increased susceptibility to infection).
  • Depending on the metastatic site, nerve damage, movement disorders, lymphedema, and skin ulceration may occur.
  • Regular blood tests and imaging tests before and during treatment are necessary to monitor treatment response and toxicity.
• Precautions for self-management
  • Inform the medical staff of all prescription medications and supplements being taken (because of the risk of drug interactions).
  • If a wound or ulcer develops, keep it clean and avoid excessive pressure or trauma.
  • Seek medical attention immediately if emergency symptoms such as fever, severe pain, or bleeding occur.

Checklist Before an Outpatient Visit (Including Recommended Items to Bring and Example Questions)

• Items to bring (recommended)
  • A list of all medications currently being taken (including prescription drugs, herbal medicines, and nutritional supplements)
  • Previous medical certificates and biopsy reports (pathology reports), and CDs or reports from previous imaging tests (CT/MRI/PET, etc.)
  • A pain and symptom diary (when symptoms began, aggravating and relieving factors, and pain severity), and records of weight changes
  • Allergies (medications and contrast media) and major medical history (surgery, heart disease, etc.)
• Information that is useful to prepare for the outpatient visit
  • When symptoms began and how they have progressed, and their impact on daily life (limited movement, walking, etc.)
  • Whether chemotherapy or radiation therapy was recently received and any adverse effects experienced
• Information to tell the doctor in advance during the outpatient visit
  • Whether acute symptoms are present (high fever, severe pain, or bleeding)
  • Possibility of pregnancy (for women) and whether breastfeeding
• Example questions before the outpatient visit (items for patients to check themselves)
  • Have the symptoms suddenly worsened recently?
  • Have any of the medications you are currently taking been changed?

General Example Questions to Ask the Doctor

• Can the primary site of this soft tissue metastasis be identified? Are additional tests (genetic testing, PET, etc.) needed?
• In my case, is complete surgical resection possible? What functional loss can be expected with resection?
• How is suitability for targeted therapy or immunotherapy determined? Should related molecular testing be performed?
• What is the expected treatment schedule, and what are the major adverse effects of each treatment? How can the adverse effects be managed?
• What rehabilitation and supportive treatments are available for quality of life (pain and motor function)?

Examples of Condition-Specific Questions

• If the primary cancer is unknown: “What additional tests do you recommend to find the primary lesion (e.g., PET-CT, endoscopy, or additional biopsy)?”
• When considering local resection: “In my case, with a solitary soft tissue metastasis (or limited metastases), how likely is complete resection to improve my prognosis? What is the risk of recurrence, and what is the follow-up testing plan?”