Primary Lingual Colonic-Type Adenocarcinoma: A Rare and Emerging Distinct Entity!

Primary colonic-type adenocarcinoma involving the tongue (CTAT) is exquisitely rare, with only four cases having been reported in the literature. We report the case of a 53-year-old woman with an anterior (oral) tongue mass. A review of literature was performed. Histomorphologic features were evaluated with standard hematoxylin and eosin stained sections. Ancillary testing was performed. The mass consisted of invasive adenocarcinoma associated with "dirty necrosis", akin to the phenotype seen in colorectal adenocarcinoma. By immunohistochemistry, the tumor cells were positive for AE1/3, CDX2, CK20, SATB2 and beta-catenin. This was initially felt to represent a metastatic colorectal adenocarcinoma but subsequent PET/CT and colonoscopy examination were negative for colorectal mass, excluding the possibility of a metastasis and confirming a diagnosis of CTAT. We raise awareness of the existence of this entity and recommend that metastatic disease be excluded before rendering a diagnosis of CTAT.