E1788. Roadmap to the Primary: Head and Neck Oncologic Lymphadenopathy
There is up to 80.4% concordance between theoretical lymphatic drainage pathways and lymphoscintigraphy in certain cancers (6). It then stands to reason that awareness of the normal lymphatic drainage pathways in the head and neck is particularly useful for subcentimeter primary lesions. The purpose of this exhibit is to review the lymph node stations in the head and neck and provide a road map to guide the neuroradiologist to the primary lesion.
Educational Goals / Teaching Points
Level I lymph nodes drain the floor of the mouth, lips, and oral tongue. Submental nodes (level Ia) typically drain into submandibular nodes (level Ib), which in turn usually drain into level II. The intraparotid nodes receive drainage from the pinna, external auditory canal, eustachian tube, buccal mucosa and gums, and skin overlying the temporalis and lateral forehead. The parotid nodes typically drain into level II/III. The sinonasal and pharyngeal mucosa usually drain to the retropharyngeal lymph nodes, which in turn drain to level II/III. Facial nodes drain to the internal jugular chain (II/III/IV). Within the internal jugular chain the drainage pathway is posterior and downwards from II to III to IV. Occipital and mastoid nodes drain to level V. The lateral neck and parietal scalp drain to level V as well. The thyroid, larynx, trachea, esophagus, and dermal lymphatics of the anterior neck drain to level VI. Level VI in turn drains to level IV and the superior mediastinum. The skin of the anterolateral neck, internal jugular chain, spinal accessory chain, subclavicular nodes, and anterior upper chest wall drain into the transverse cervical chain. We will also discuss some exceptions to these rules.
Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
When patients present with cervical lymphadenopathy of unknown cause, the preferred initial imaging exam in adults is a CT Neck with contrast. Characteristics of pathologic lymph nodes include: loss of the fatty hilum and loss of the normal kidney bean shape in addition to using size criteria. In general, cervical lymph nodes are considered pathologic above 1 cm in short axis. In cases where MRI happens to be the initial study, key sequences are: T1, T2 fat saturation or STIR, and post-contrast T1 fat saturation sequences. Saturation pulses are important to reduce vascular pulsation artifacts.
Knowledge of the lymphatic drainage pathway is extremely useful in hunting down the primary lesion in head and neck cancer and helps improve diagnostic accuracy when interpreting CT Neck exams in patients presenting with de novo lymphadenopathy.