Lymph Node Metastasis

Cervical metastatic lymph nodes are most commonly from squamous cell carcinoma of the head and neck. Other primary neoplasms include skin cancer, thyroid cancer, and with a lower frequency, lung, breast, and abdominal malignancies. Lymphoma also can involve the head and neck. Lymphomatous nodes are typically homogeneous, but can occasionally be necrotic, particularly after therapy and occasionally prior to therapy, especially in Hodgkin’s disease and Burkitt lymphoma. Squamous cell carcinoma metastatic lymph nodes are often heterogeneous, with cystic or necrotic areas, and can have irregular margins, which are suggestive of extracapsular spread.

Imaging Criteria That Are Suggestive of Malignancy

• Short axis diameter >1 cm: Except the jugulodigastric nodes, which most authors say can be slightly larger, and the lateral retropharyngeal nodes, which are of concern when over 6 mm in the setting of known malignancy. The use of different size criteria at different levels to improve sensitivity (8, 9, 6, 7 mm for levels 1 to 4 and lower, respectively) has been suggested. Criteria may be different in N0 neck because by using these standard size criteria there is a relatively low sensitivity for metastatic disease. The use of 7 mm for level 2 and 6 mm for the remainder of the neck has been suggested.
  
• Rounded nodes with a ratio of the long axis to short axis <2
  
• Central necrosis (important to distinguish from a normal fatty hilum, which tends to be peripheral)
  
• Heterogeneous architecture
  
• Cystic neck mass in adult
  
• Calcification may be benign or malignant; if malignant, most commonly papillary thyroid carcinoma
  
• Extracapsular spread (poorly defined margins, adjacent infiltration, or fat stranding)
  
• Grouping of three or more 8 to 10 mm nodes in a primary drainage pathway
  
• Decreased iron oxide uptake (when imaging with supersmall ultraparamagnetic iron oxide contrast media)
  
• Increased metabolic activity on F18-fluorodeoxyglucose positron emission tomography (FDG PET)

Causes of Nonmalignant Adenopathy

Some rare conditions are mentioned, as it is important to consider them as they can mimic malignancy. Biopsy is generally required for diagnosis.