The use of monoclonal anti-CEA antibody immunohistochemistry in detecting the origin of oral cavity metastasis.

A 75-year-old woman presented with a painless swelling in the right mandibular retromolar area and numbness of the left lower lip. Radiographic examination of the mandible demonstrated an osteolytic lesion of the ascending ramus. Biopsy revealed adenocarcinoma of obscure origin. Staining of the specimen with a monoclonal antibody specific to colon carcinoma revealed its origin. On subsequent examinations, a primary tumor in the rectosigmoid region with extensive lung, liver and skeletal metastases were diagnosed. This unusual case of colonorectal carcinoma, presenting as a metastatic lesion of the mandible, was readily diagnosed by a novel immunohistochemical technique that utilizes highly specific monoclonal antibodies.