Imaging of Laryngeal and Hypopharyngeal Squamous Cell Cancers

This article provides a comprehensive overview of imaging in the evaluation of laryngeal and hypopharyngeal squamous cell carcinomas. It highlights the critical role of computed tomography (CT), MR imaging, and PET/CT in staging, treatment planning, and surveillance. Key anatomic landmarks, patterns of tumor spread, imaging features relevant to TNM staging, and post-treatment changes are discussed. Emphasis is placed on identifying imaging findings that alter management, such as subsite evaluations, cartilage invasion, extralaryngeal extension, and regional nodal metastasis. The article also addresses common diagnostic challenges and pearls for accurate interpretation.

Key points

•
Understanding laryngeal and hypopharyngeal anatomy is key to assessing tumor extent, spread, and staging on cross-sectional imaging.
•
Cross-sectional imaging is essential for evaluating deep tumor spread, tissue invasion, and nodal disease, complementing endoscopy in staging and treatment planning.
•
Following therapy, imaging is essential for detecting recurrent disease and distinguishing it from expected postradiation or postsurgical changes, often requiring a multimodality approach.

Abbreviations

CT	computed tomography
ENE	extranodal extension
NIRADS	Neck Imaging Reporting and Data System
tvc	true vocal cord

Introduction

Laryngeal and hypopharyngeal squamous cell carcinomas (SCCs) account for less than 20% of head and neck cancers and predominantly affect men between the ages of 50 and 70. The primary risk factors are tobacco and alcohol use, although human papillomavirus is an emerging contributor in a subset of cases. This review focuses on the role of imaging for diagnosis, staging, and post-treatment evaluation, which plays a critical role in the choice of therapy, which is a combination of chemoradiation and surgery.

Anatomy

A thorough understanding of this complex anatomy is essential for accurately interpreting cross-sectional imaging, as the patterns of tumor spread and staging are closely tied to these distinct anatomic compartments.

The larynx serves as both the airway and the voice box, extending from the oropharynx above to the trachea below, and situated anterior to the hypopharynx. It is divided into 3 anatomic regions: the supraglottis, glottis, and subglottis. The supraglottis extends from the tip of the epiglottis to the level of the laryngeal ventricle and contains key structures including the epiglottis, aryepiglottic folds, false vocal cords, portions of the arytenoid cartilages, and the pre-epiglottic and paraglottic spaces. The glottis spans approximately 1 cm inferiorly from the laryngeal ventricle to the lower margin of the true vocal cords and includes the true vocal cords along with the anterior and posterior commissures. The subglottis lies below, extending from the undersurface of the true vocal cords to the inferior border of the cricoid cartilage ( Box 1 , Figs. 1–4 ).

Box 1

Imaging anatomy and implications

True vocal cord (tvc)	Includes vocal ligament and thyroarytenoid muscle	Crucial for sound production. Fixation implies tumor involvement of the tvc or cricoarytenoid joint
Pre-epiglottic and paraglottic spaces	Anterior to epiglottis and lateral to glottis	Crucial in the spread of laryngeal malignancies; involvement upstages cancer to T3 and increases the occurrence of metastatic lymphadenopathy
Laryngeal saccule	Outpouching from the anterosuperior portion of laryngeal ventricle, between the vestibular fold and thyroid cartilage and contains mucous glands to lubricate vocal folds	Secondary laryngocele due to obstruction by glottic or supraglottic carcinoma
Conus elasticus	Fibroelastic membrane extending superiorly from cricoid to the medial margin of tvc	Acts as a relative barrier to the spread of malignancies from the glottis downward
Lymphatics	Supraglottis: rich in lymphatics	Prone to bilateral nodal spread
	Glottis: sparse lymphatics	Small tumors rarely cause nodal spread
	Subglottis: less dense lymphatics compared with supraglottis	Drains primarily to central compartment nodes
Nerve supply	Recurrent laryngeal nerve innervates all intrinsic muscles of larynx except cricothyroid muscle which is supplied by superior laryngeal nerve	The pathway of the nerves affects both the surgical approach and potential complications

A set of axial C T scans shows labeled cross-sections of the head and neck, including the hyoid, pharyngeal muscles, airways, and various structures, with letters indicating key regions. — Fig. 1

A pair of labeled C T scan sections presents anatomical structures in the head and neck, with abbreviations marking features such as h, s m, p e s, p g s, l v, t, t v c, c, and others. — Fig. 2

A series of sagittal C T scans of the neck has displayed labeled structures including the hyoid, epiglottis, vocal cords, trachea, and cervical vertebrae, with airway and pharyngeal regions. — Fig. 3

A pair of anatomical diagrams illustrates labeled parts of the larynx and pharynx on the left and a cross-sectional view of the neck with labeled structures on the right. — Fig. 4

The larynx is suspended from the hyoid bone and supported by a cartilaginous framework composed of 3 unpaired cartilages (epiglottis, thyroid, and cricoid) and 4 paired cartilages (arytenoid, corniculate, cuneiform, and triticeous). The thyroid and cricoid cartilages provide the primary structural support, whereas the corniculate, cuneiform, and triticeous cartilages, though part of the framework, have limited clinical significance ( Box 2 , see Figs. 1–4 ).

Box 2

Cartilages and clinical significance

Cartilages	Features	Clinical Significance
Thyroid	Shield shaped-lamina, superior and inferior cornua, offers pathway for tumor spread through attachments like the thyrohyoid membrane to hyoid	Protects vocal cords, essential for voice production; tumor invasion here can affect voice and require complex treatment approaches
Thyroid	The vocal ligaments attach anteriorly to the inside of the thyroid cartilage	Lack of perichondrium at the site of attachment and relatively narrow distance between the mucosa and thyroid cartilage increase the vulnerability for tumor invasion
Cricoid	Signet ring shaped, only complete ring of cartilage, provides foundational support for the larynx. Cricothyroid membrane connects to thyroid cartilage	Involvement in tumors often precludes voice preservation surgeries due to its structural role in the larynx
Epiglottis	Leaf-shaped stalk (petiole) and free portion. Perforations in the cartilage is susceptible to tumor invasion. Hyoepiglottic and thyroepiglottic ligament connects to hyoid and thyroid cartilage	Closes the laryngeal inlet preventing food entry into the airway during swallowing; its invasion by tumors can compromise this function
Arytenoid	Pyramid-shaped base, vocal process, lateral process and apex. Articulates with the cricoid via synovial joints	Key for vocal cord functionality; changes or invasions here can affect voice modulation and breathing

The hypopharynx links the oropharynx to the esophagus and communicates directly with the laryngeal inlet. It begins at the posterior aspect of the pharyngoepiglottic folds, near the inferior margin of the hyoid bone, and extends inferiorly to the cricopharyngeus muscle, which encircles the junction between the hypopharynx and the esophagus at the level of the cricoid cartilage (see Figs. 1–4 ).

Anatomically, the hypopharynx is subdivided into 3 principal subsites: the pyriform sinuses, the posterior wall, and the postcricoid region (see Fig. 1 ). The pyriform sinuses create bilateral recesses that envelop the larynx. Each pyriform sinus extends from the pharyngoepiglottic folds inferiorly to the level of the true vocal cords, bordered medially by the aryepiglottic folds and laterally by the thyroid cartilage and thyrohyoid membrane. The posterior hypopharyngeal wall is a direct continuation of the posterior wall of the oropharynx, while the postcricoid region represents the lower anterior hypopharyngeal wall, situated posterior to the cricoid cartilage and collapsing against the posterior wall when not distended. From a clinical perspective, tumors involving the posterior wall are particularly aggressive, with a higher propensity for bilateral cervical lymph node metastases.

Imaging techniques

Imaging plays a crucial role in determining the extent of the tumor, its spread to nearby tissues or organs, and the presence of metastases. The role of the commonly used imaging is summarized in Box 3 .

Box 3

Overview of imaging modalities

Imaging Modality	Advantages	Disadvantages	Usage
Computed tomography (CT)	Widely available Fast imaging time that mitigates patient’s motion High resolution for assessing cartilage invasion and lymph nodes	Suboptimal soft tissue contrast Equivocal thyroid cartilage invasion due to age-related variations in cartilage mineralization	Commonly first imaging choice
MR imaging	Superior soft tissue contrast Multiparametric tissue characterization For assessment of prevertebral space, esophageal involvement	Longer imaging time that is prone to motion artifact	Often used in equivocal CT assessment of cartilage or paraglottic space invasion and tumor delineation that is crucial for surgical or radiation planning
FDG PET-CT or PET-MR imaging	Metabolically active tumors, regional and distant metastases that is undetectable by CT/MR imaging	False positive of inflammation	In advanced disease, treatment response assessment and detecting recurrence
Ultrasound	Useful in evaluating vocal cord mobility and lymph nodes	Operator-dependence	Valuable for assessing and guiding biopsy of suspicious lymph nodes

Each imaging technique has its strengths and limitations, and often complementary to provide a comprehensive assessment. The choice of imaging often depends on the stage of the disease, the patient’s condition, and institutional preferences with the aims for accurate staging, appropriate treatment plan, and predicting prognosis. Both computed tomography (CT) and MR imaging should be tailored to the relevant anatomy, and the specific clinical question, utilizing a combination of both standard and available advanced techniques (dual energy, diffusion-weighted imaging, contrast-enhanced perfusion imaging, arterial spin labeling techniques when available). Some of these advanced techniques will be covered by other authors in this issue.

Tumor staging

Imaging evaluation of laryngeal and hypopharyngeal SCC requires a thorough understanding of the AJCC TNM staging—the extent of the main tumor (T), the spread to nearby lymph nodes (N), and distant metastasis (M). The initial clinical staging relies on presurgical assessments (physical examinations, imaging), while the pathologic staging is determined by examining the resected tissue from the surgery.

The stages of laryngeal and hypopharyngeal cancers are slightly different and are summarized in Boxes 4 and 5 . In laryngeal cancer, key detections that upstage to T3 disease are any of these findings: fixation of vocal cord; invasion of the pre-epiglottic and/or paraglottic space; invasion of the inner cortex of thyroid cartilage. Tumor erosion of the outer cortex of thyroid cartilage, tumor involvement of the cricoid, and/or extralaryngeal soft tissue further upstages to T4a disease. Both laryngeal and hypopharyngeal T4b is generally considered unresectable disease when tumor invades the prevertebral space, mediastinum, and/or encases the carotid.

Box 4

Laryngeal carcinoma staging

Adapted from Itamura K, Hsue VB, Barbu AM, et al. Diagnostic assessment (imaging) and staging of laryngeal cancer. Otolaryngol Clin N Am 2023;56(2):215–31.

TX and Tis
TX and Tis are the same for all 3 sites of the larynx
- •
  TX : primary tumor cannot be assessed
- •
  Tis : carcinoma in situ
T1, T2, and T3
T1 through T3 are defined differently by laryngeal site:
Supraglottis
- •
  T1 : limited to one subsite of supraglottis, with normal vocal cord mobility:
  - ○
    Suprahyoid epiglottis
  - ○
    Aryepiglottic folds, laryngeal aspect
  - ○
    Infrahyoid epiglottis
  - ○
    False vocal cords (ventricular folds/bands)
  - ○
    Arytenoids
- •
  T2 : invades mucosa of more than one adjacent area, with normal vocal cord mobility:
  - ○
    Subsite of supraglottis
  - ○
    Glottis
  - ○
    Region outside supraglottis, for example, base of tongue, vallecula, medial wall of pyriform sinus
- •
  T3 : limited to larynx with vocal cord fixation and/or invasion of any of the following:
  - ○
    Inner cortex of thyroid cartilage
  - ○
    Paraglottic space
  - ○
    Pre-epiglottic space
  - ○
    Postcricoid area
Glottis
- •
  T1 : limited to vocal cord(s) with normal vocal cord mobility (may involve anterior or posterior commissure)
  - ○
    T1a : limited to one vocal cord
  - ○
    T1b : involves both vocal cords
- •
  T2 : extends to supraglottis and/or subglottis, and/or with impaired vocal cord mobility
- •
  T3 : limited to larynx with vocal cord fixation and/or invasion of paraglottic space and/or inner cortex of thyroid cartilage
Subglottis
- •
  T1 : limited to subglottis
- •
  T2 : extends to vocal cord(s) with normal or impaired vocal cord mobility (no cord fixation)
- •
  T3 : limited to larynx with vocal cord fixation and/or invasion of paraglottic space and/or inner cortex of thyroid cartilage
T4
T4 is the same for all 3 sites of the larynx:
- •
  T4 : moderately or very advanced
  - ○
    T4a : moderately advanced local disease:
    - ▪
      Invades through outer cortex of thyroid cartilage
    - ▪
      Invades cricoid cartilage
    - ▪
      Invades tissues beyond the larynx (eg, trachea, deep extrinsic muscles of the tongue, strap muscles, thyroid gland, esophagus)
  - ○
    T4b : very advanced local disease:
    - ▪
      Invades the mediastinum
    - ▪
      Invades the prevertebral space
    - ▪
      Encases the carotid artery
Regional lymph node (N)
- Regional nodal status is defined the same as for most other cancers of the head and neck. See the main article, cervical lymph node (staging).
Distant metastases (M)
- The following categories may be used, either in the clinical classification (c) for patients with cancer identified before treatment and/or in the pathologic classification (p) for patients for whom surgery is the first definitive therapy:
  - •
    cM0 : no evidence of metastases
  - •
    cM1 : distant metastasis
  - •
    pM1 : distant metastasis, microscopically confirmed
Clinical nodal status (cN)
- Clinical criteria apply for patients treated nonsurgically, without cervical lymph node dissection. Clinical evaluation synthesizes information from such sources as physical examination, imaging, and fine-needle aspiration.
  - •
    NX : nodes cannot be assessed
  - •
    N0 : no regional node metastases
  - •
    N1 : metastasis in single ipsilateral node, ≤3 cm, and no extranodal extension (ENE(−))
  - •
    N2
    - ○
      N2a : metastasis in single ipsilateral node, >3 cm and ≤6 cm, and ENE(−)
    - ○
      N2b : metastasis in multiple ipsilateral nodes, all ≤6 cm, and ENE(−)
    - ○
      N2c : metastasis in bilateral or contralateral nodes, all ≤6 cm, and ENE(−)
  - •
    N3
    - ○
      N3a : metastasis in a node, >6 cm, and ENE(−)
    - ○
      N3b : metastasis in a node with clinically overt ENE(+) (ENE _c)
Pathologic nodal status (pN)
- Pathologic criteria apply for patients treated surgically, with cervical lymph node dissection, for whom multiple whole lymph nodes are available for microscopic evaluation.
  - •
    NX : nodes cannot be assessed
  - •
    N0 : no regional node metastases
  - •
    N1 : metastasis in single ipsilateral node, ≤3 cm, and no extranodal extension (ENE(−))
  - •
    N2
    - ○
      N2a : metastasis in single ipsilateral node, >3 cm and ≤6 cm, and ENE(−); or metastasis in single ipsilateral node, ≤3 cm, and ENE(+)
    - ○
      N2b : metastasis in multiple ipsilateral nodes, all ≤6 cm, and ENE(−)
    - ○
      N2c : metastasis in bilateral or contralateral nodes, all ≤6 cm, and ENE(−)
  - •
    N3
    - ○
      N3a : metastasis in a node, >6 cm, and ENE(−)
    - ○
      N3b : metastasis in single ipsilateral node, >3 cm, and ENE(+); or multiple ipsilateral, contralateral, or bilateral nodes any with ENE(+); or single contralateral node of any size and ENE(+)