What is the difference between posterolateral neck dissection (PLND) and modified radical neck dissection (MRND) in terms of indications and outcomes?

Posterolateral Neck Dissection versus Modified Radical Neck Dissection

Posterolateral neck dissection (PLND) is a specialized procedure reserved exclusively for malignant epithelial tumors of the posterior scalp with occult or clinically manifest nodal metastases in the posterior cervical triangle, whereas modified radical neck dissection (MRND) is a comprehensive neck dissection used for therapeutic management of clinically positive cervical lymph node metastases (N1-N2 disease) in head and neck squamous cell carcinomas. 1, 2

Anatomic Coverage and Indications

Posterolateral Neck Dissection

• PLND addresses the posterior cervical triangle lymph nodes (levels V and posterior structures), specifically targeting drainage patterns from posterior scalp lesions 2
• This procedure may be performed alone or combined with MRND when both anterior and posterior nodal basins are at risk 2
• The primary indication is posterior scalp malignancies, not oral cavity, pharyngeal, or laryngeal primaries 2
• In the original validation series, PLND demonstrated excellent local control with 5 of 13 electively treated patients (38%) showing occult metastases, justifying its use for clinically N0 posterior scalp lesions 2

Modified Radical Neck Dissection

• MRND is a comprehensive dissection removing all lymph node levels (I-V) that would be included in a radical neck dissection while preserving one or more non-lymphatic structures (sternocleidomastoid muscle, internal jugular vein, or spinal accessory nerve) 1, 3
• Contemporary guidelines classify MRND as a "comprehensive" neck dissection rather than using older terminology 1, 3
• For N1-N2 disease in head and neck squamous cell carcinoma, MRND provides appropriate therapeutic nodal clearance 1, 4
• For N3 disease, comprehensive neck dissection (which may be MRND or radical neck dissection) is recommended 3, 1

Site-Specific Applications

Oral Cavity Primaries

• MRND for oral cavity cancers with nodal metastases must include levels I-IV, with level I dissection being essential 1, 3
• For N0 oral cavity disease, selective neck dissection of at least levels I-III is appropriate rather than MRND 3

Pharyngeal and Laryngeal Primaries

• MRND for oropharyngeal and hypopharyngeal primaries should address levels II-IV, with level I potentially omitted 1, 3
• For laryngeal cancers, levels II-IV and level VI (when appropriate, particularly for infraglottic lesions) should be included 3, 1

Posterior Scalp Lesions

• PLND is the appropriate procedure, not MRND, unless anterior nodal basins are also involved 2

Outcomes and Efficacy

PLND Results

• In posterior scalp malignancies, PLND achieved 100% local control during mean 47-month follow-up, with only 1 of 3 regional recurrences occurring within the previously dissected field 2

MRND Results

• MRND combined with postoperative radiotherapy achieved 91% regional control for pathologically N2/N3 disease, demonstrating equivalence to radical neck dissection 4
• MRND appears as effective as radical neck dissection even for advanced neck disease (N2/N3), supporting preservation of the spinal accessory nerve whenever oncologically feasible 4
• The most common MRND modification is spinal accessory nerve preservation 4

Critical Decision Points

When to Choose PLND

• Use PLND only for malignant epithelial tumors of the posterior scalp 2
• Consider combined PLND + MRND when both posterior scalp primary and anterior nodal involvement coexist 2

When to Choose MRND

• Use MRND for clinically positive nodes (N1-N2) in oral cavity, oropharyngeal, hypopharyngeal, or laryngeal squamous cell carcinomas 1, 3
• For bilateral disease or midline tumors, bilateral neck dissections are often necessary 1, 3

When to Avoid MRND

• For N0 disease, selective neck dissection is preferred over MRND 3
• For N3 disease, comprehensive dissection is required, which may necessitate radical rather than modified radical approach depending on extent of disease 3, 1

Important Caveats

• A properly performed MRND should yield 10 or more lymph nodes for pathologic examination 1
• When MRND is performed as salvage after failed primary treatment, complication rates increase significantly, including delayed wound healing, skin necrosis, and carotid exposure 1
• MRND complications occur in approximately 41% of patients versus 25% for selective procedures 5
• The terminology "comprehensive" versus "selective" is now preferred over "modified radical" in contemporary guidelines, though MRND remains a valid comprehensive dissection 3, 1