A case of oral metastasis of rectal adenocarcinoma with KRAS mutation in patient with synchronous lung adenocarcinoma

Detecting the origin of the primary cancer that metastasizes in the oral cavity in patients with multiple primary cancers is challenging because of its rarity and complexity. We present an unusual case of an 86‐year‐old women with a maxillary gingival tumor that was histologically proven to be adenocarcinoma; she had been diagnosed with rectal and lung adenocarcinoma. A multidisciplinary approach involving complementary molecular analysis of KRAS gene mutation helped in the diagnosis of metastatic gingival tumor from rectal cancer.