What structures are typically included in the flap raised during a Modified Radical Mastectomy (MRM)?

Flap Raised in Modified Radical Mastectomy (MRM)

Direct Answer

In a Modified Radical Mastectomy, the flap raised typically includes skin and subcutaneous tissue overlying the breast, preserving the pectoralis major muscle while removing breast parenchyma, the nipple-areolar complex, and axillary lymph nodes. 1

Anatomical Components of the MRM Flap

Structures Included in the Flap

• Skin envelope: The overlying breast skin is elevated as part of the flap, though the extent varies based on whether skin-sparing techniques are employed 1
• Subcutaneous tissue: The subcutaneous fat layer between skin and breast parenchyma is preserved in the flap 1
• Superficial fascia: This layer remains attached to the undersurface of the skin flaps 2

Structures Removed (Not Part of the Preserved Flap)

• Breast parenchyma: All breast tissue is removed, including the nipple-areolar complex in standard MRM 1
• Axillary lymph nodes: Level I and II axillary nodes are dissected and removed 1
• Pectoralis minor muscle: May be resected (Patey technique) or preserved (Madden technique), though this is not part of the "flap" per se 3

Technical Considerations

Muscle Preservation

• The pectoralis major muscle is preserved in MRM, distinguishing it from radical mastectomy 2, 3
• The pectoralis minor muscle handling varies: it may be resected or preserved without affecting surgical outcomes, lymph node yield, or complication rates 3
• Preservation of the pectoralis major maintains chest wall contour and function while allowing adequate axillary dissection 2

Flap Thickness and Viability

• The flap should be raised with adequate thickness to maintain blood supply to the skin 4
• Residual breast tissue may remain in the skin and subcutaneous layers, which is why recurrences can occur in these areas (reported in the majority of post-mastectomy recurrences) 1
• The flap is elevated off the pectoralis major fascia, creating a potential space that requires drainage 4

Clinical Implications

For Reconstruction Planning

• Skin-sparing mastectomy preserves most of the original skin envelope for immediate reconstruction, removing only the nipple-areolar complex and previous biopsy sites 1
• The preserved skin flaps provide the foundation for both implant-based and autologous tissue reconstruction 1
• Adequate flap thickness is critical for successful reconstruction outcomes, particularly when radiation therapy is planned 1

Common Pitfalls

• Inadequate flap thickness can compromise skin viability and increase necrosis risk 4
• Overly aggressive flap elevation may leave residual breast tissue, increasing local recurrence risk 1
• In inflammatory breast cancer specifically, skin-sparing approaches are contraindicated due to dermal lymphatic involvement 1

Postoperative Management

• The dead space created between the flap and chest wall typically requires drainage, with optimal removal when output is below 50 mL per 24 hours 4
• Seroma formation is the most common complication in the space beneath the flap 1, 4