Nonsalivary Primary Adenocarcinomas of the Base of the Tongue A Single Tertiary-Care Oncology Center Series of 6 Cases

Context.-Nonsalivary primary adenocarcinomas of the base of the tongue (PABOTs) are extremely rare and worth reporting.Objective.-To study the detailed clinicopathologic features of PABOT.Design.-Cases of PABOT diagnosed on pathology material were retrieved from the archived electronic surgical pathology records.Results.-Six cases in 4 men and 2 women (M:F ratio, 2:1), with an age range of 31 to 76 years, satisfied the criteria. The tumor epicenter was the base of the tongue in all (6 of 6; 100%), with extension to the epiglottis in 50% (3 of 6), nodal metastasis in 66.7% (4 of 6), and distant metastasis in 33.3% (2 of 6). On histology, all but one were pure adenocarcinoma. Five of 6 cases (83.3%) had a gastrointestinal (GI) phenotype, of which 2 (40%) had a colonic/lower-GI-type (small groups of cells floating in mucin, CK20 thorn , SATB2 thorn , and CDX2 thorn ) and 3 (60%) had an upper-GI-like adenocarcinoma (UGI-LA; malignant glands with intracellular mucin, CK7 thorn ) histology. Cystic structure suggestive of teratomatous origin was identified in 2 of 5 cases (40%), both with UGI-LA phenotype. The non-GItype case had a unique histology with squamous differentiation in addition to adenocarcinoma areas, diffuse nuclear b-catenin on immunohistochemistry, and a corresponding exon 3 CTNNB1 mutation. One patient succumbed to disease, and 4 are alive with disease (follow-up of 1-9 months after completion of therapy).Conclusions.-We suggest using the broad term primary adenocarcinomas of the base of tongue (PABOTs), which can be further subdivided into colonic-type adenocarcinoma of the tongue and oral cavity, UGI-LA, and not otherwise specified categories, and reiterate a need for recognition and distinction of PABOT from salivary gland tumors. A subset originates from teratoid/duplication cysts, necessitating extensive sampling. Multicentric studies are essential to clinically and biologically prognosticate each of these categories.