Retroauricular Lymph Nodes: Anatomy, Drainage, and Clinical Significance

Retroauricular lymph nodes (also called postauricular or mastoid nodes) are a group of superficial lymph nodes located posterior to the ear, over the mastoid process.

Anatomy

• Number: 2–4 nodes (variable)
• Location: Superficial to the mastoid fascia, posterior to the auricle, anterior to the sternocleidomastoid attachment
• Drainage (Afferent):
  • Posterolateral scalp (parietal/occipital)
  • External auditory canal, tympanic membrane
  • Pinna (especially posterior surface)
  • Eyelids (lateral), conjunctiva
  • Parotid region (superficial)
• Efferent drainage: → Superior deep cervical nodes (jugulodigastric) → Jugular trunk

Clinical Significance

Lymphadenopathy Causes

• Local infection: Otitis externa, mastoiditis, scalp cellulitis, infected ear piercing, herpes zoster (Ramsay Hunt)
• Skin malignancy: Melanoma, SCC, BCC of scalp, ear, face (sentinel node basin)
• Viral: Rubella, EBV, CMV, HIV – often generalized but retroauricular prominent
• Reactive: Seborrheic dermatitis, psoriasis of scalp
• Lymphoma: Primary or secondary involvement

Examination

• Palpate gently with fingertips behind the ear, comparing sides
• Note size (<1 cm normal), consistency (soft/rubber = reactive; hard/fixed = malignant), mobility, tenderness
• Examine scalp, ear, parotid, and other nodal basins (preauricular, cervical, occipital)

Imaging and Biopsy

• Ultrasound: Cortical thickness >3 mm, loss of hilum, rounded shape suggest malignancy
• FNA or excisional biopsy if >1 cm persistent >2–4 weeks, hard, fixed, or constitutional symptoms
• Sentinel lymph node biopsy (SLNB) for melanoma/SCC of scalp/ear maps to retroauricular/parotid nodes

Retroauricular nodes are a key sentinel site for scalp/ear malignancies and a localizing sign for otologic and scalp infections.