Phyllodes tumor of the breast

Disease Description (Causes and Symptoms)

• Definition: A phyllodes tumor of the breast is a rare connective-tissue tumor with a benign–borderline–malignant spectrum, characterized by a leaf-like pattern within the lesion. It is classified as benign, borderline, or malignant according to histologic findings (such as stromal cellularity, mitotic pattern, and atypia).
• Cause: The exact cause is unknown.
• Pathophysiology summary: Tumor growth and invasiveness (or lack thereof) are primarily determined by the proliferation and mitotic activity of the stromal component. When classified as malignant, it may show local invasion and, rarely, hematogenous metastasis (to the lungs, bones, etc.).
• Main symptoms and features:
  • Usually a painless, rapidly growing (over weeks to months), firm breast lump with relatively well-defined margins
  • Size varies widely (approximately 1–41 cm; average approximately 4–7 cm)
  • In large tumors, the skin may become stretched or thinned, superficial vessels may become visible, or ulceration may occur
  • Axillary lymph node metastasis is rare
• Diagnostic clues: A mobile, well-defined mass on clinical examination; a well-circumscribed lesion on imaging (mammography, ultrasound, and MRI); and core needle biopsy can aid diagnosis (fine-needle aspiration (FNA) has a high likelihood of false-negative results).

Treatment Methods and Precautions

• Surgery:
  • The definitive treatment is surgical removal.
  • Small benign lesions are treated with wide excision including the tumor and sufficient normal breast tissue (according to the provided guidance, some examples recommend a margin of 2 cm or more, but many institutions aim for a clear resection margin of at least 1 cm). The extent of excision is determined by the size and shape of the lesion.
  • For large tumors or those diagnosed as borderline or malignant, total mastectomy (simple mastectomy) may be necessary, and breast conservation is often difficult.
  • Axillary lymph node dissection is generally not recommended (lymph node metastasis is rare).
• Radiation therapy:
  • Adjuvant radiation therapy may be considered when the risk of local recurrence is high (such as in borderline or malignant tumors, recurrent lesions, or very large tumors), but evidence of its effectiveness has not been fully established.
• Systemic therapy:
  • The effectiveness of chemotherapy and hormone therapy has not been established. In cases of metastatic malignant phyllodes tumor, individualized discussion in consultation with a medical oncologist is necessary (systemic chemotherapy may sometimes follow an approach used for soft-tissue sarcomas).
• Follow-up and lifestyle management:
  • Regular follow-up examinations are necessary because local recurrence is possible after surgery (reported in approximately 15–20% of cases after surgery; higher in malignant tumors).
  • If the tumor grows rapidly or skin changes (redness, ulceration, bleeding, etc.) develop, visit a hospital promptly.
• Complications:
  • Local recurrence, scarring and breast deformity caused by surgery, and, rarely, distant metastasis from malignant lesions (to the lungs, bones, etc.).
• Clinical considerations:
  • Because prognosis varies according to pathologic findings (stromal cellularity, mitotic count, etc.), plans for additional treatment and follow-up are established based on pathology results before and after surgery.
  • Securing an adequate resection margin is an important factor in reducing the risk of recurrence.

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

• Recommended items to bring:
  • A list of currently used medications (including prescription drugs, over-the-counter medications, and supplements)
  • Past medical history, history of surgery and anesthesia, and allergy information
  • Reports or CDs from previous breast imaging examinations (mammography, ultrasound, and MRI)
  • Copies of previous biopsy (needle biopsy or excisional biopsy) and pathology reports
  • Photos showing changes in the size or shape of the lump (if taken by the patient)
  • Family history related to breast disease (such as familial breast cancer)
• Symptom record:
  • When the lump was first noticed and changes in its size (when it began and how quickly it grew)
  • Presence of pain, skin changes, or discharge
• Key points to explain to the doctor during the visit:
  • When symptoms related to the lump began and how they have changed
  • Previous examination and treatment history
  • Whether you wish to preserve the breast (cosmetic considerations)

Examples of General Questions to Ask the Doctor

• "What additional tests are needed to determine definitively whether my lesion is benign, borderline, or malignant?"
• "What resection margin is recommended for surgery? Is breast conservation possible?"
• "What is the likelihood of recurrence after surgery? If it recurs, how will treatment differ?"
• "Do I need radiation therapy or chemotherapy in my case? What side effects may occur?"

Examples of Disease-Specific Questions

• "According to my pathology report, what were the stromal cellularity and mitotic count, and based on these findings, what is my grade (benign/borderline/malignant)?"
• "If the resection margin obtained during surgery is insufficient, is additional surgery or radiation therapy recommended? How are the recommended criteria (margin width) applied?"