Background: Carcinoembryonic antigen (CEA) is a cell surface glycoprotein which is overexpressed in various cancers but reported prevalence data vary considerably for many tumor types. Because of its overexpression in various cancer types and the limited expression in normal tissue CEA has become a potential drug target with several potential drug candidates currently being evaluated. CEA is also shed into the blood stream, so that CEA measurement in the serum is used as a tool for early detection and recurrence monitoring of cancer. Methods: To comprehensively determine CEA expression in normal and neoplastic tissues, a tissue microarray containing 15,413 samples from 120 different tumor types and subtypes as well as 76 different normal tissue types were analyzed by immunohistochemistry. Results: CEA was detectable in 65 (54.2%) of 120 tumor categories including 49 (40.8%) tumor types with at least one strongly positive case. CEA positivity was most common in colorectal adenomas (100%) and carcinomas (98.7%), other gastrointestinal adenocarcinomas (61.1%-80.3%), medullary carcinomas of the thyroid (96.3%), pulmonary adenocarcinoma (73.7%), mucinous carcinomas of the ovary (79.8%) and the breast (43.2%), squamous cell carcinomas of various sites (30.2%-69.1%), and small cell carcinomas of the lung (64.3%), the urinary bladder (38.9%), and the prostate (50.0%) as well as non-invasive papillary urothelial carcinoma pTa G3 (33,6%), pTa G2 high-grade (25,0%) and pTa G2 low-grade (5,7%). High CEA expression was linked to high grade tumors (p < 0.0001) and invasive growth (p < 0.0001) in urinary bladder cancer as well as estrogen receptor positivity (p = 0.0005) and HER2 positivity (p = 0,0158) in invasive breast cancer of no special type. In 1.250 colorectal adenocarcinomas, reduced CEA expression was associated with mismatch repair deficiency (p < 0.0001) but not with pT and pN stage. CEA expression level was unrelated to clinico-pathological tumor parameters in adenocarcinomas of the pancreas and the stomach, endometroid endometrium carcinoma as well as in serous and endometroid carcinomas of the ovaries. Conclusions: In summary, CEA is abundantly expressed in a broad range of epithelial neoplasms. Our data thus identify various tumor entities where CEA positive cancers might best benefit from CEA serum monitoring and anti-CEA therapies.