Laryngeal Cancer

• Fast Facts:  Covered here.
• Indications for PET/CT: Covered here.
• Imaging Protocol: Covered here.

Patient Presentations:

• The majority of patients with laryngeal cancer have a biopsy-proven diagnosis prior to PET/CT scanning. In such cases, any focus of FDG uptake involving the larynx is usually the cancer (prior to therapy).
• Many patients will present with the diagnosis of metastatic SCCA of unknown primary.  A laryngeal primary must be excluded in these patients.
• Lastly, on rare occasion, an incidental laryngeal cancer will be identified.

Criteria for “Active Malignancy”: 

• As previously discussed (here), the vocal cords and laryngeal structures normally demonstrate little or no metabolic activity.  
• Nearly all laryngeal cancers arise in either the glottic larynx (true vocal cords, anterior and posterior commissures) or the supraglottic larynx (epiglottis, arytenoids, aryepliglottic folds, false cords) and present as a focal area of increased FDG uptake. When an accompanying soft tissue mass is clearly present on the co-registered images, the diagnosis is easy to make.  
• Not infrequently, an accompanying soft tissue lesion does not clearly accompany focal increased laryngeal uptake (especially when intravenous contrast is not administered).  The absence of a soft tissue abnormality should not preclude a suspicion for malignancy when a focus of FDG uptake is noted in the larynx. We typically report:

  • “ A subcentimeter of intense FDG uptake is noted to involve the anterior commissure of the glottic larynx (SUV 4.6). Although an associated soft tissue lesion is not clearly demonstrated on the co-registered non-contrast images, the appearance is suspicious for a primary laryngeal carcinoma. Direct visualization is strongly recommended in this case.”

• Obviously, the presence of associated hypermetabolic cervical nodes dramatically increases the likelihood of malignancy (and the confidence of your reporting). 

False Positives in Vocal Cord Uptake:

• Bilateral Uptake:
  • If a patient speaks after FDG injection (patients routinely sneak out their cell phones and have lengthy conversations), the vibrating vocal cords and cricoarytenoid muscles can become intensely avid. Consequently, bilateral intense uptake in the vocal cords and/or cricoarytenoid muscles is considered normal — in the absence of an associated CT abnormality.

• Unilateral Cord Uptake in Contralateral Cord Paralysis:
  • While a unilateral hot vocal cord may represent a primary laryngeal cancer, not infrequently it reflects normal physiologic uptake in a patient with contralateral vocal cord paralysis, who has vocalized after FDG injection (addressed in detail, here). The paralyzed vocal cord will be non-avid, while the normal “vocalizing” vocal cord will appear hot.

In such cases, the diagnosis is confirmed on the CT images, where the paralyzed side will typically demonstrate thickening and medial positioning of the aryepiglittic fold, dilatation of the pyriform sinus and vallecula, anterior positioning of the arytenoid cartilage, and prominence of the affected vocal cord.