Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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December 5, 2024
Adenoid Cystic Carcinoma of the Esophagus
- Background:
- Adenoid cystic carcinoma (ACC) of the esophagus is a rare malignant tumor that arises from the salivary gland–like cells of the esophageal submucosal glands. ACC accounts for less than 1% of esophageal malignancies and has a predilection for the distal esophagus. On imaging, ACC typically appears as a well-defined, round or oval-shaped mass with a smooth contour that may be located in the submucosal or muscular layers of the esophagus. Endoscopically, ACC may appear as a submucosal mass with overlying intact mucosa, or it may be visible as a polypoid or ulcerative lesion. The histologic appearance of ACC is characterized by a biphasic growth pattern, with both epithelial and myoepithelial components. The epithelial component forms duct-like structures, while the myoepithelial component has a spindle cell or stellate appearance. The tumor cells may show perineural invasion, and metastases may occur late in the disease course, often to the lungs, liver, or bones.
- Clinical Presentation:
- These are usually asymptomatic, until their growth causes dysphagia, or their perineural dissemination causes vocal cord paralysis.
- Key Diagnostic Features:
- CT: ACC may show as a iso/hyperdense mass with irregular serrated borders, homogeneous enhancement, calcification, and surrounding bony erosion.
- MRI: On T1-weighted images ACC shows isointense signal, on T2-weighted images iso/hipointense (mostly variable) signal and mild homogeneous enhancement with IV contrast administration. Furthermore, MRI is excellent to determine perineural invasion, showing neural enlargement and enhancement.
- Differential Diagnosis:
- Leiomyoma: On CT, leiomyomas appear as well-circumscribed, smooth, homogeneous masses with attenuation similar to that of muscle. On MRI, they appear hypointense on T1-weighted images and hyperintense on T2-weighted images. On endoscopic studies, leiomyomas typically appear as submucosal masses with intact overlying mucosa. They can be difficult to differentiate from ACC on imaging alone, but can often be distinguished by their lack of enhancement and characteristic "whorled" appearance on histology.
- Squamous cell carcinoma (SCC): On CT, SCC typically presents as a long segmental stricture with circumferential thickening and irregular mucosal surface. On MRI, SCC appears as a low-signal-intensity mass on T1-weighted images and high-signal-intensity mass on T2-weighted images. On endoscopic studies, SCC appears as an irregular, ulcerated mass with friable surface. It can be differentiated from ACC by its lack of glandular structures and characteristic squamous differentiation on histology.
- Gastrointestinal stromal tumor (GIST): On CT, GISTs appear as well-circumscribed, homogeneous masses with variable enhancement. On MRI, they appear hypointense on T1-weighted images and hyperintense on T2-weighted images. On endoscopic studies, GISTs appear as submucosal masses with intact overlying mucosa. They can be differentiated from ACC by their characteristic expression of CD117 and other immunohistochemical markers.
- Adenocarcinoma: On CT, adenocarcinoma typically presents as a long segmental stricture with circumferential thickening and irregular mucosal surface. On MRI, adenocarcinoma appears as a low-signal-intensity mass on T1-weighted images and high-signal-intensity mass on T2-weighted images. On endoscopic studies, adenocarcinoma appears as an irregular, ulcerated mass with friable surface. It can be differentiated from ACC by its lack of cribriform or tubular glandular structures on histology.
- Lymphoma: On CT, esophageal lymphoma can present as a focal mass or diffuse thickening of the esophageal wall with homogeneous enhancement. On MRI, lymphoma appears iso- or hypointense on T1-weighted images and hyperintense on T2-weighted images. On endoscopic studies, lymphoma can appear as a smooth, infiltrative mass or diffuse thickening of the esophageal wall. It can be differentiated from ACC by its lack of glandular structures and characteristic lymphoid proliferation on histology.
- Metastases: On CT, metastases may have varying degrees of enhancement, ranging from hypo- to hyperattenuating compared with the adjacent esophageal wall. On MRI, they are typically T2 hyperintense and may show variable enhancement patterns on contrast-enhanced sequences.
- Treatment:
- The first-line treatment for esophageal adenoid cystic carcinoma is radical resection with negative margins and regional lymph node dissection. Radiotherapy has been suggested if the surgical margins are positive for tumor involvement, but traditional chemotherapy is ineffective. Multiple local recurrences are usually seen after surgical treatment.
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