Overview
Definition:
Lymphadenectomy, also known as lymph node dissection, is the surgical removal of lymph nodes
It is a crucial component in the staging and treatment of various cancers, aiming to remove potentially metastatic cancer cells and assess nodal involvement for prognosis and further management
The extent and technique of lymphadenectomy are highly dependent on the primary tumor's histology, location, and presumed lymphatic drainage patterns.
Epidemiology:
The incidence of requiring lymphadenectomy varies widely with the type of cancer
Cancers like breast cancer, melanoma, lung cancer, and head and neck cancers frequently involve lymph node metastasis, making lymphadenectomy a standard part of treatment
The importance of sentinel lymph node biopsy (SLNB) has reduced the morbidity of complete lymph node dissection in early-stage diseases, but remains dependent on tumor type.
Clinical Significance:
Accurate lymphadenectomy is vital for accurate cancer staging (TNM system), which directly influences treatment decisions, prognosis, and patient outcomes
Inadequate dissection can lead to undertreatment and recurrence, while overly aggressive dissection can result in significant morbidity, including lymphedema, infection, and nerve damage
Understanding tumor-specific lymphatic spread is paramount for optimizing surgical strategy.
Indications
General Indications:
Cancer with a high propensity for lymphatic metastasis
Clinical or radiologic evidence of lymph node involvement
To confirm nodal status for staging and treatment planning
Therapeutic removal of gross nodal metastases
Prophylactic removal of at-risk lymph nodes.
Specific Tumor Considerations:
Tumor histology dictates the lymphatic pathways and risk of metastasis
For example, melanoma and breast cancer have predictable lymphatic drainage, while some sarcomas can spread randomly
The primary tumor's grade and stage also influence the decision for lymphadenectomy.
Role Of Imaging And Biopsy:
Imaging modalities like CT, MRI, PET-CT, and ultrasound help identify suspicious lymph nodes
Fine needle aspiration cytology (FNAC) or core needle biopsy can confirm nodal metastasis pre-operatively
Sentinel lymph node biopsy (SLNB) is indicated in select cases (e.g., early breast cancer, melanoma) to identify the first draining lymph node, minimizing unnecessary dissection.
Contraindications:
Distant metastatic disease where lymphadenectomy would not be curative
Patient with severe comorbidities making surgical intervention too risky
Presence of extensive nodal involvement rendering complete clearance impossible or detrimental.
Lymphadenectomy By Tumor Type
Breast Cancer:
Axillary lymph node dissection (ALND) or sentinel lymph node biopsy (SLNB)
ALND typically involves removing levels I, II, and III nodes
SLNB is preferred for clinically node-negative patients to assess for micrometastases.
Melanoma:
Sentinel lymph node biopsy (SLNB) is the standard of care for clinically node-negative patients with intermediate to high-risk melanomas
If SLNB is positive, completion lymph node dissection (CLND) of the involved basin is considered, though its therapeutic benefit is debated and often replaced by adjuvant therapy.
Head And Neck Cancers:
Neck dissection (e.g., radical, modified radical, selective) is guided by tumor location, size, and clinical nodal status
Specific dissections target specific nodal levels (I-VI) based on expected drainage patterns for oral cavity, pharyngeal, and laryngeal cancers.
Gastric Cancer:
D2 lymphadenectomy is the standard, involving dissection of nodes along the major gastric vessels and their branches (stations 1-12)
The extent depends on tumor location and depth of invasion
Greater omentectomy is usually included.
Colorectal Cancer:
D3 lymphadenectomy, involving resection of mesentery with lymph nodes along the major mesenteric vessels (e.g., SMA, IMA), is performed for advanced disease or high-risk features
Standard colectomy involves dissection of regional lymph nodes along the associated vascular pedicles.
Lung Cancer:
Mediastinal lymph node dissection (MLND) is crucial for staging and treatment
This includes stations 2, 4, 7, 8, 9 (for lung apex), and other stations based on tumor location
Systematic sampling or complete dissection is performed, often during thoracotomy or VATS.
Prostate Cancer:
Pelvic lymphadenectomy, ranging from limited to extended dissections, is performed for staging and risk stratification, particularly in intermediate to high-risk disease
It influences adjuvant therapy decisions
Nodes removed include obturator, external iliac, and internal iliac groups.
Surgical Techniques And Principles
Principles Of Oncologic Dissection:
Maintain anatomical integrity of vascular and nerve structures
Ensure complete removal of lymphatic tissue within the defined nodal basin
Prevent tumor spillage during dissection
Adequate specimen orientation for pathological analysis.
Sentinel Lymph Node Biopsy Technique:
Involves preoperative injection of a tracer (e.g., technetium-99m colloid or vital blue dye) near the primary tumor
The first draining lymph node(s) (sentinel nodes) are identified using a gamma probe and/or visual inspection and excised for pathological examination.
Complete Lymph Node Dissection Technique:
Systematic removal of all lymph nodes and surrounding fatty tissue within a defined anatomical compartment
Techniques vary based on the region and include open, laparoscopic, or robotic approaches.
Morbidity And Prevention:
Common morbidities include lymphedema, seroma formation, wound infection, and nerve injury
Careful surgical technique, meticulous hemostasis, appropriate drainage, and patient education are essential for prevention.
Intraoperative Considerations:
Choice of energy device to minimize thermal spread
Accurate identification of critical structures
Specimen handling to avoid crushing
Decision-making regarding positive sentinel nodes or unexpected findings.
Pathological Evaluation
Importance Of Pathology:
Accurate pathological assessment of excised lymph nodes is critical for staging, prognosis, and guiding adjuvant therapy
It determines the presence, number, and extent of nodal metastases.
Reporting Standards:
Pathology reports should include the total number of nodes examined, number of positive nodes, location of positive nodes within the basin, and status of extranodal extension (ENE)
Nodal station identification is crucial for specific cancers.
Special Stains And Immunohistochemistry:
Immunohistochemistry (e.g., CK7, CK20, TTF-1, PSA, Melan-A, S-100) can aid in identifying metastatic deposits from unknown primary tumors or confirming the origin of metastatic cells within lymph nodes.
Definition Of Micrometastasis And Macrometastasis:
Micrometastases are typically defined as deposits of cancer cells < 0.2 mm or < 2 mm, often detected by immunohistochemistry
Macrometastases are larger and visible microscopically without special stains.
Postoperative Care And Follow-up
Early Postoperative Management:
Wound care, pain management, monitoring for complications like bleeding, infection, or seroma
Early mobilization is encouraged.
Lymphedema Management:
Education on limb elevation, compression garments, manual lymphatic drainage, and exercises
Avoidance of trauma or infection to the affected limb.
Surveillance Strategies:
Regular clinical examination, imaging (e.g., CT, PET-CT), and tumor markers to detect recurrence or new primary tumors
Frequency and modality depend on the primary cancer and stage.
Adjuvant Therapy Decisions:
Based on pathological findings (especially nodal status and ENE), patients may receive adjuvant chemotherapy, radiation therapy, or targeted therapy to reduce the risk of recurrence.
Key Points
Exam Focus:
Understand the rationale behind lymphadenectomy for common cancers
Know the specific nodal stations relevant to each cancer type (e.g., SEER, AJCC)
Differentiate indications for SLNB vs
complete lymphadenectomy
Recognize common complications and their management.
Clinical Pearls:
Always consider the patient's overall health and potential for morbidity when deciding on the extent of lymphadenectomy
The goal is oncologic control with acceptable functional outcomes
Accurate specimen handling and communication with pathology are paramount.
Common Mistakes:
Inadequate nodal dissection (undertreatment)
Overly aggressive dissection leading to excessive morbidity
Incorrect identification of nodal basins
Failure to consider SLNB when indicated
Poorly documented pathology reports regarding lymph node status.