Hypopharynx Squamous cell carcinoma

• Solid soft tissue nodule or region of asymmetric superficial thickening in the piriform sinus (66-75% of cases) on CT or MRI
• Obliteration of normal fat planes around the hypopharynx suggesting tumor extension beyond the pharyngeal confines
• Cervical lymph node metastases present in up to 75% of patients at diagnosis
• T2 intermediate-to-high signal mass on MRI that enhances on T1 post-gadolinium imaging

• On CT: primary tumor appears as a solid soft tissue nodule or region of superficial thickening with increased enhancement; most common location is piriform sinus (66-75% of cases), followed by posterior pharyngeal wall and postcricoid/pharyngo-esophageal junction.
• On CT: when tumor extends beyond pharyngeal confines, surrounding fat planes become obliterated; however fat stranding may reflect inflammatory response rather than tumor invasion, requiring careful correlation with clinical findings.
• On MRI: primary tumor demonstrates intermediate-to-low signal on T1-weighted images and intermediate-to-high signal on T2-weighted sequences.
• On MRI: following gadolinium administration, tumor enhancement is usually present; larger tumors and nodal metastases may show central necrosis.
• On barium swallow fluoroscopy: small sessile or superficially spreading lesions are difficult to visualize, while larger lesions appear as irregular filling defects or cause asymmetric narrowing.
• Careful cervical lymph node assessment is essential as up to 75% of patients present with nodal metastases at diagnosis.
• FDG-PET demonstrates metabolically active tumor deposits; useful for identifying distant disease but limited by lesion size threshold and motion artifact.
• Post-irradiation imaging is challenging due to edematous irradiated mucosa and soft tissue fibrosis that may obliterate normal fat planes and mimic tumor recurrence.

• Non-squamous cell malignancy (adenocarcinoma, small cell carcinoma) — differentiation based on histology and may have different enhancement patterns.
• Accessory salivary gland tumor — typically more circumscribed mass without the same aggressive infiltration and obliteration of fat planes.
• Lymphoma — typically involves multiple sites, may have different signal characteristics, and lacks the local invasive features.
• Radiation change from prior irradiation — presents as edema and fibrosis without true mass effect; clinical history and stability on follow-up imaging help distinguish from recurrence.
• Retropharyngeal abscess — demonstrates restricted diffusion on DWI-MRI, lacks the enhancing mass, and may show fluid-fluid levels.
• Benign pharyngeal stenosis or stricture — does not demonstrate the enhancing soft tissue mass or nodal metastases.

Describe the location of the primary tumor (piriform sinus vs. posterior wall vs. postcricoid), the size of the enhancing mass, presence or absence of fat plane obliteration, and explicitly characterize cervical lymph nodes by level and size; state whether findings are concerning for local extension versus inflammatory change, noting that post-treatment changes require comparison with prior studies to assess for true recurrence.

• Overestimating tumor extent based on fat plane obliteration alone, which can reflect inflammation rather than true invasion—clinical correlation is essential.
• Missing small superficial lesions on barium swallow; negative barium does not exclude early SCC, and cross-sectional imaging (CT or MRI) should be pursued for symptomatic patients.
• Misinterpreting post-radiation edema and fibrosis as residual or recurrent tumor; comparison with prior imaging and stability on follow-up are critical to distinguish post-treatment changes from true disease.
• Underestimating the high frequency of cervical lymph node metastases (75% at presentation)—meticulous nodal assessment and characterization are essential for accurate staging and prognosis.