What is the best approach for a female patient of reproductive or post-menopausal age with a large fibroepithelial neoplasm (benign tumor of the breast) with myxoid (mucous-like) changes, and no significant medical history: monitoring or excision?

Management of Fibroepithelial Neoplasm with Myxoid Changes

For a fibroepithelial neoplasm with myxoid changes, monitoring is acceptable for select patients with imaging-pathology concordance, but excision should be strongly considered given the myxoid features which raise concern for phyllodes tumor. 1

Key Decision Points

When Monitoring is Appropriate

Monitoring may be suitable if all of the following criteria are met:

• Complete imaging-pathology concordance exists between the core needle biopsy findings and imaging characteristics 1
• The lesion is small (≤2 cm) and has remained stable in size 2, 3
• No concerning clinical features such as rapid growth, skin changes, or palpable mass characteristics suggesting phyllodes tumor 4, 3
• Patient has low anxiety about the lesion and accepts close surveillance 2

If monitoring is chosen, the NCCN recommends:

• Physical examination with or without ultrasound/mammogram every 6-12 months for 1-2 years 1
• Immediate surgical excision if the lesion increases in size or clinical suspicion rises 1

When Excision Should Be Performed

Excision is strongly recommended in the following scenarios:

• Myxoid changes on core biopsy - this histologic feature is associated with phyllodes tumors and warrants complete excision to exclude borderline or malignant phyllodes tumor 4, 5
• Large size (>2 cm) - masses ≥4 cm have significantly higher rates of phyllodes tumor (38% in one study) 2, 3
• Rapid growth or recent size increase - sudden enlargement is characteristic of phyllodes tumors 4, 3
• Imaging-pathology discordance - any mismatch between biopsy findings and imaging characteristics mandates excision 1
• Patient anxiety or request for removal - this is a valid indication per multiple guidelines 2
• Dense or heterogeneous appearance on imaging - higher density correlates with phyllodes tumor risk 3

Critical Clinical Pitfalls

The Phyllodes Tumor Problem

Core needle biopsy cannot reliably distinguish fibroadenoma from phyllodes tumor - the biphasic nature and stromal characteristics may not be adequately sampled 4, 3. In one study, 38% of fibroepithelial lesions on core biopsy proved to be phyllodes tumors on final excision 3.

Myxoid changes specifically raise concern because:

• Myxoid stroma is a recognized feature of phyllodes tumors, including benign variants 4
• Even "benign" phyllodes tumors can recur locally if incompletely excised 5, 6
• Borderline phyllodes tumors can have satellite nodules beyond the apparent tumor margin 5

Size Matters

Median size of masses containing phyllodes tumors was 4 cm versus 2.4 cm for those without (P < 0.002) 3. Large fibroepithelial lesions warrant excision regardless of benign appearance on imaging 2, 3.

Surgical Approach if Excision is Chosen

• Wide local excision with negative margins is the standard approach 5, 6
• For giant lesions (>10 cm), simple mastectomy may be required 4, 7
• Axillary dissection is not indicated unless there is pathologic evidence of nodal involvement 7
• Re-excision for positive margins is debated for benign/borderline lesions, as recurrence rates are low (3%) even with positive margins 6, but satellite foci can occur 5

Post-Excision Management

• If final pathology confirms simple fibroadenoma without atypia, return to routine age-appropriate screening 2
• If benign phyllodes tumor with clear margins, routine surveillance without adjuvant therapy 7
• If borderline or malignant phyllodes tumor, oncology referral for consideration of radiation therapy 4