Background: ACC is a relatively rare tumor of epithelial cell origin, most commonly arising from major or minor salivary glands, and comprises 3 to 5% of all head and neck malignancies.
Primary adenoid cystic carcinoma (ACC) in the peri-esophageal region is a rare entity. ACC in this location could be either arising from minor salivary gland tissue or seromucinous glands in the trachea or esophagus with the involvement of surrounding soft tissue causing pressure effect on other organs. Kaur et al reviewed 11 cases of ACC arising from the trachea, of which one case presented as difficulty in swallowing and two experienced hoarseness of voice (1). Sawada et al report 36 cases of ACC arising primarily from the esophagus (2).
Pathology: Diagnosis of ACC presenting as a mass in an uncommon location as in the peri-esophageal region may be challenging. Imaging cannot differentiate ACC from other tumors such as neuroendocrine tumors, paraganglioma, and pleomorphic adenoma in this location (1,3). Fine needle aspiration (FNA) remains a well-accepted procedure in the preoperative diagnosis of lesions as it is cost-effective, minimally invasive, and highly accurate. Accurate FNA diagnosis of ACC in an unusual location is greatly aided by the characteristic cytomorphology which shows variable cellularity with cohesive clusters and sheets of basaloid cells surrounding dense hyaline globules . These basaloid cells are uniform with oval and angulated hyperchromatic nuclei and scant cytoplasm (4,5). In our case, the tumor showed a typical cytology pattern of ACC and thus did not present a diagnostic problem.
The histologic feature of ACC is the presence of a cribriform, nested, trabecular, and solid type of arrangement of cells. These nests typically composed of two cell types: small basaloid myoepithelial cells and ductal epithelial cells. The proportion of each component varies among different tumors. The cribriform spaces may contain homogeneous, amorphous eosinophilic material. This pink material may stain with alcian blue and Periodic Acid-Schiff stain (1, 6). In our case, biopsy findings showed tumor cells arranged in a cribriform and tubular pattern surrounding eosinophilic hyaline material, which is a characteristic feature of ACC.