We report a cribriform carcinoma of the left fossa poplitea in a 62-year-old woman. The patient did not present any symptoms, and the only complaint was the nodule, which was resected for diagnosis. After considering different diagnostic options, we decided that the most appropriate one was cribriform carcinoma, which is an entity described in 1998. The diagnostic criteria, which were provided in the few publications that refer to this entity, helped us to distinguish it from the main mimicker: cystic adenoid carcinoma. Owing to the cribriform pattern of the tumor, we also looked for a metastasis from other sites, mainly breast, vulva, and salivary glands, but all these were clinically excluded. The tumoral cells showed secretion by decapitation, as well as a positive stain of the luminal secretion by histochemical techniques of Alcian blue and periodic acid-Schiff. The tumor was negative for iron stain. In spite of these characteristics, which are, for some authors, indicative of an apocrine phenotype, the immunohistochemical study revealed some differences with the profile that has been described in cases of apocrine adenocarcinoma. The tumor did not express GCDFP-15 or CD 15. It was also negative for SMA, CEA, and PR. The pattern of cytokeratins expressed by our case was positive for AE1-AE3, CAM 5.2, and CK7, without any expression for CK20. Other markers expressed by the tumor were EMA, ER, c-erbB-2, p53, and S-100.