What is a modified radical mastectomy (MRM)?

Modified Radical Mastectomy: Definition and Technique

Modified radical mastectomy (MRM) is a surgical procedure for breast cancer that removes the entire breast and ipsilateral axillary lymph nodes while preserving one or both pectoral muscles, distinguishing it from radical mastectomy which removes the pectoralis major muscle. 1, 2

Anatomical Components Removed

• The entire breast tissue including the nipple-areolar complex is excised 2, 3
• Axillary lymph node dissection is performed, typically yielding approximately 20 lymph nodes for pathological examination 2
• The pectoralis major muscle is preserved in all modern MRM techniques 2, 4, 3
• The pectoralis minor muscle may be either preserved (Madden technique) or resected (Patey technique), with no significant difference in outcomes between these approaches 2

Technical Variations

There are two primary technical approaches that differ only in handling of the pectoralis minor muscle:

• Madden technique: Preserves both pectoralis major and minor muscles, providing excellent cosmetic results and arm function while maintaining oncologic adequacy 2, 3
• Patey technique: Preserves pectoralis major but resects pectoralis minor muscle 2

Research demonstrates these techniques are equivalent in terms of surgical duration (approximately 102-105 minutes), lymph node yield (19-20 nodes), complication rates, and surgical difficulty, allowing surgeon discretion in technique selection 2

Axillary Dissection Approach

• Complete axillary dissection extends from the subclavicular region to the lateral border of the latissimus dorsi muscle 3
• The dissection can be performed through dual approaches: from the subclavicular point down to the pectoralis minor, and from the posterior aspect of the pectoralis minor laterally 3
• Parasternal lymph node dissection can be added for centrally or medially located tumors in Stage II-IIIa disease 3

Critical Prerequisite: Metastatic Screening

• MRM should only be performed in the absence of distant metastases, as metastatic disease represents an absolute contraindication to proceeding directly with this surgery 1
• A metastatic screen must be completed as a standard first step before surgical planning 1
• In Stage IV disease, a minimum of 4-6 months of neoadjuvant systemic therapy is required before any surgical consideration 1

Important Distinction

• Do not confuse modified radical mastectomy with modified radical mastoidectomy, which is an entirely different otologic procedure for ear disease in a completely different anatomic region 5

Postoperative Management

• One medial-to-lateral (pectoro-axillary) drain with low negative pressure represents the optimal drainage approach, with removal on postoperative day 2-3 or when output falls below 50 mL per 24 hours 6
• Average hospitalization duration is 2.3 days 2
• Post-mastectomy radiation to the chest wall and regional lymphatics is mandatory when surgery is performed, with dose escalation to 66 Gy for patients >45 years, close/positive margins, ≥4 positive nodes, or poor response to preoperative treatment 1

Functional and Cosmetic Outcomes

• Preservation of the pectoralis major muscle provides superior cosmetic appearance and arm function compared to radical mastectomy 4, 3
• The procedure facilitates easier breast reconstruction if desired, though immediate reconstruction must be avoided in Stage IV disease and delayed until completion of all therapy 1