What is the appropriate evaluation and management of a patient presenting with a reactive lymph node in the groin area?

Evaluation and Management of Groin Reactive Lymph Node

For a reactive groin lymph node, observation with clinical monitoring is the standard approach, but fine-needle aspiration (FNA) should be performed if the node is moderately enlarged, heterogeneous on imaging, or persists beyond 4-6 weeks to exclude malignancy. 1, 2

Initial Clinical Assessment

Perform a focused examination evaluating:

• Node characteristics: size (measure diameter), mobility versus fixation, unilateral versus bilateral presentation, and relationship to surrounding structures 3
• Search for primary lesions: examine the lower extremity skin, perineum, genitalia, and anus for potential malignancies or infectious sources 2, 4
• Constitutional symptoms: fever, night sweats, weight loss suggesting systemic disease 2
• Duration of lymphadenopathy: nodes persisting beyond 4-6 weeks warrant tissue diagnosis 5

Critical point: 30-50% of palpable groin lymphadenopathy is inflammatory rather than malignant, so do not assume malignancy without tissue confirmation 2, 4

Diagnostic Algorithm

For Simple Reactive Lymphadenopathy (Small, Mobile, Soft Nodes)

• Treat underlying infection if suspected with appropriate antibiotics 1
• Observe for 4-6 weeks with clinical re-examination 1
• If nodes resolve, no further workup needed 5

For Concerning Features (Enlarged >1.5 cm, Firm, Fixed, or Heterogeneous)

Proceed immediately to FNA as the mandatory first diagnostic step with sensitivity of 91.7% and specificity of 98.2% for detecting malignancy 2

If FNA is negative but clinical suspicion remains high (heterogeneous appearance, persistent enlargement):

• Perform excisional biopsy for definitive diagnosis, as FNA can miss micrometastases 2

If FNA is positive for malignancy:

• Proceed immediately with disease-specific oncologic management 2
• For penile or vulvar cancer: immediate inguinofemoral lymph node dissection 3, 1
• For melanoma: complete lymphadenectomy per melanoma protocols 2

Imaging Considerations

Ultrasound with Doppler is the first-line imaging modality for groin lymph nodes with the following suspicious features: 3, 6, 7

• Longitudinal/transverse diameter ratio <2 (sensitivity 81% for metastasis) 7
• Absent echogenic fatty hilum (specificity 95% for malignancy) 3, 7
• Eccentric or irregular cortex (specificity 96% for malignancy) 7

US-guided FNA should be performed on the largest or most abnormal node if suspicious features are present, increasing diagnostic accuracy to 93% sensitivity and 100% specificity 3

CT or MRI is reserved for:

• Assessment of pelvic lymph nodes when ≥2 positive inguinal nodes are confirmed 4
• Evaluation of primary tumor extent in known malignancy 3

Common Pitfalls to Avoid

Do not proceed to immediate surgical excision without FNA first - this causes unnecessary morbidity and delays diagnosis 2

Do not assume all palpable nodes are malignant - up to 50% are inflammatory, and reactive lymphadenopathy typically resolves spontaneously within weeks 2, 5

Do not miss micrometastases - up to 25% of clinically negative lymph nodes harbor occult metastases in patients with known primary malignancies, emphasizing the importance of pathologic staging 3, 1

Do not delay treatment in confirmed malignancy - subsequent groin relapses after inadequate initial treatment are rarely salvageable 3, 1

Follow-Up Strategy

For confirmed reactive lymphadenopathy:

• Address the underlying infectious or inflammatory cause 2
• Monitor node size and characteristics clinically 1
• Consider repeat biopsy if nodes enlarge, become fixed, or develop concerning features 2

For malignancy:

• Follow disease-specific oncologic protocols with regular clinical examination 1
• Imaging intervals per cancer type guidelines 2