Pitfalls in the Staging Squamous Cell Carcinoma of the Hypopharynx Amy Y. Chen, MDa, Patricia A. Hudgins, MDb,* KEYWORDS Squamous cell carcinoma Hypopharynx Aryepiglottic fold Larynx KEY POINTS To accurately interpret pretreatment and posttreatment imaging in patients with hypopharyngeal squamous cell carcinoma (SCC), one must understand the complex anatomy of this part of the aerodigestive system. Common patterns of spread must be recognized. Pitfalls in imaging must be understood. This article reviews the epidemiology, anatomy, staging, treatment and pitfalls in imaging of hypo- pharyngeal SCC. INTRODUCTION AND EPIDEMIOLOGY statistically the most common malignancy of the hypopharynx. Alcohol potentiates the mutagenic Compared with laryngeal neoplasms, primary effects of tobacco. The biology of HP SCC is inter- hypopharyngeal (HP) tumors, especially those esting, and an area of ongoing study. Mutations in exclusively in the HP subsites, are relatively un- the p53 tumor suppressor gene are more common common, accounting for about 4% of all head in HP SCC than in other head and neck sites.2,3 and neck tumors. Tumors of the hypopharynx Field carcinogenesis, the concept that carcino- are generally advanced stage when detected, gens affect surrounding tissue that has yet to be and have often already extended to the larynx or transformed to tumor, also is common in HP cervical esophagus. Imaging is critical in staging SCC. Thus tumors may be multicentric, spread these advanced primary tumors for guiding treat- submucosally, and be very difficult to stage with ment planning, and because locoregional control imaging or endoscopy alone. At presentation may be difficult to attain, accurate staging is espe- tumors are often at an advanced stage, and the cially critical. rich lymphatic drainage of the hypopharynx and Epidemiology is difficult to report, as laryngeal cervical esophagus result in frequent nodal metas- and oral-cavity squamous cell carcinoma (SCC) tases. The role of human papillomavirus (HPV) in statistics are often lumped together with HP 1 HP SCC is still being determined, but early numbers. Patients are generally older than 50 evidence suggests HPV infection is less commonly years, and men are more commonly affected involved in SCC of HP than are oropharyngeal than women at a rate of 3:1. Tobacco and alcohol subsites.4,5 abuse are the risk factors responsible for SCC, a Department of Otolaryngology-Head & Neck Surgery, Emory University School of Medicine, 1364 Clifton Road, Northeast Atlanta, GA 30322, USA; b Department of Radiology and Imaging Sciences, Division of Neuro- radiology, Head & Neck Section, Emory University School of Medicine, BG-27, 1364 Clifton Road, Northeast, Atlanta, GA 30322, USA * Corresponding author. Department of Head and Neck Radiology, Emory University School of Medicine, Atlanta, GA 30322. E-mail address: [email protected] Neuroimag Clin N Am 23 (2013) 67–79 http://dx.doi.org/10.1016/j.nic.2012.08.007 1052-5149/13/$ – see front matter Ó 2013 Elsevier Inc. All rights reserved. neuroimaging.theclinics.com 68 Chen & Hudgins A rare but well-described syndrome of upper Another helpful way to understand HP anatomy esophageal webs, iron-deficiency anemia, and is to know the individual subsite anatomy. The 3 postcricoid HP SCC is Plummer-Vinson syndrome. HP subsites are the pyriform sinuses, lateral and Patients are usually Caucasian women between 40 posterior HP walls, and the postcricoid region. and 70 years of age. Better nutrition including iron The pyriform sinuses are paired, right and left, supplementation has led to a marked decrease in and they extend from the pharyngoepiglottic folds this syndrome.6 of the suprahyoid epiglottis to the inferior cricoid cartilage. For each pyriform sinus, the lateral NORMAL ANATOMY AND BOUNDARIES border is the lateral pharyngeal wall and the medial border is the aryepiglottic fold, specifically the HP To conceptualize HP anatomy, one must under- surface of the aryepiglottic fold. The pyriform stand that the larynx and the hypopharynx are so sinuses are shaped like upside down pyramids, interrelated that it is impossible to know the with the apex located at the true vocal cord level. anatomy of one without understanding the other. So even if they are collapsed and not filled with A simplified concept is that the larynx is immedi- air, if the axial image is at the true vocal cord or ately anterior with respect to the hypopharynx, arytenoid cartilage level, each pyriform sinus forms the anterior wall of the hypopharynx, and apex is posterior and lateral. The pyriform sinus the larynx “bulges into” the anterior aspect of the is the most common location for HP SCC, hypopharynx. Boundaries of the hypopharynx are accounting for about 60% of all cases. often described as they relate to laryngeal sub- The second subsite, the posterior HP wall, is the sites. The craniocaudal boundaries are quite inferior extension of the posterior wall of the specific: the superior boundary is at a plane at oropharynx. This portion extends to the postcri- the hyoid bone level, and the inferior boundary is coid subsite of the hypopharynx. the lower border of the cricoid cartilage (Fig. 1). The postcricoid portion of the hypopharynx, also As such, the hypopharynx is that portion of the the caudalmost region, is accurately named as aerodigestive tract between the oropharynx (supe- located posterior to the cricoid cartilage, extend- rior) and the proximal cervical esophagus (inferior). ing from the posterior wall of the hypopharynx at The hyoid bone and cricoid are parts of the laryn- the cricoarytenoid joint level to the inferior cricoid geal skeleton. Immediately posterior and deep to cartilage and proximal cervical esophagus. On the hypopharynx is the retropharyngeal space. axial images, therefore, the mucosal overlying the posterior cricoid cartilage is the anterior aspect of the postcricoid HP. The posterior portion of the postcricoid HP is the cricopharyngeus muscle, which merges with the cervical esophagus. Post- cricoid tumors are the least common of HP SCC. AMERICAN JOINT COMMITTEE ON CANCER STAGING The American Joint Committee on Cancer (AJCC) staging manual should be used as a guide, as it clearly lays out the anatomic details necessary to accurately stage tumors of the hypopharynx (Table 1). Like other subsites, the difference between AJCC sixth and seventh editions is primarily the division of T4 lesions into T4a or moderately advanced disease and T4b, or very advanced local disease.7 Staging HP tumors requires both clinical and radiologic information.8 Knowledge of the specific subsites and the maximum diameter of the tumor are essential (see Table 1). A T1 tumor involves Fig. 1. Hypopharyngeal (HP) boundaries, depicted in orange. The hypopharynx extends from the posterior one subsite (posterior pharyngeal wall, pyriform pharyngeal wall (arrow) at the level of the hyoid sinus, or postcricoid hypopharynx) or is 2 cm or bone, to the proximal cervical esophagus. The hypo- smaller in greatest dimension (Figs. 2–4). A T2 tumor pharynx is posterior to the larynx and anterior to the invades another HP subsite or an adjacent site (for retropharyngeal space. (Courtesy of Eric Jablonowski.) example, a laryngeal subsite), or is greater than Pitfalls in Staging SCC of Hypopharynx 69 Table 1 AJCC 7: hypopharynx Primary Tumor (T) TX Primary tumor cannot be assessed T0 No evidence of primary tumor Tis Carcinoma in situ T1 Tumor limited to one subsite of hypopharynx and/or 2 cm or less in greatest dimension T2 Tumor invades more than one subsite of hypopharynx or an adjacent site, or measures more than 2 cm but not more than 4 cm in greatest dimension without fixation of hemilarynx T3 Tumor more than 4 cm in greatest dimension or with fixation of hemilarynx or extension to esophagus T4a Moderately advanced local disease Tumor invades thyroid/cricoid cartilage, hyoid bone, thyroid gland or central compartment soft tissue (includes prelaryngeal strap muscles and subcutaneous fat) T4b Very advanced local disease Tumor invades prevertebral fascia, encases carotid artery, or involves mediastinal structures Regional Lymph Nodes (N) NX Regional lymph nodes cannot be assessed N0 No regional lymph node metastasis N1 Metastasis in a single ipsilateral lymph node, 3 cm or less in greatest dimension N2 Metastasis in a single ipsilateral lymph node, more than 3 cm but not more than 6 cm in greatest dimension; or in multiple ipsilateral lymph nodes, none more than 6 cm in greatest dimension; or in bilateral or contralateral lymph nodes, none more than 6 cm in greatest dimension N2a Metastasis in single ipsilateral lymph node more than 3 cm but not more than 6 cm in greatest dimension N2b Metastasis in multiple ipsilateral lymph nodes, none more than 6 cm in greatest dimension N2c Metastasis in bilateral or contralateral lymph nodes, none more than 6 cm in greatest dimension N3 Metastasis in a lymph node more than 6 cm in greatest dimension Note: Metastases at level VII are considered regional lymph node metastases Distant Metastasis (M) M0 No distant metastasis M1 Distant metastasis From Edge SB, Byrd DR, Compton CC, et al. Editorial Board. AJCC Cancer staging manual. 7th edition. Chicago: Springer; 2010. p. 41–56; with permission. 2 cm but less than 4 cm (Fig. 5). By definition, there hemilarynx, usually at the insertion of the aryepi- is no fixation of the hemilarynx for a T1 or T2 tumor. glottic fold to the arytenoid cartilage (Fig. 6). Fixation of the hemilarynx is defined as im- Therefore, vocal cord motion is often impaired paired motion of the true vocal cord. For HP when the tumor is in the medial pyriform sinus. SCC, this can be a result of tumor invading the Bulky pyriform sinus carcinomas may cause hem- larynx at the cricoarytenoid joint or the intrinsic ilarynx fixation owing to a weight effect. The tumor laryngeal muscles. Thus, the vocal cord paralysis may cause arytenoid cartilage immobility at the is from tumor extending from the hypopharynx top of the cartilage, but the base is still mobile.