Fallopian tube adenofibromas (FTAs) are considered rare, but their frequency has never been determined by systematic sampling of this organ. To determine the morphological spectrum and prevalence of FTAs, we analyzed a consecutive series of fallopian tubes removed during surgery for a wide range of disorders. Fallopian tubes were completely evaluated with attention to the fimbriated end (sectioning and extensively examining the fimbria [SEE-FIM] protocol). Discrete localized subepithelial stromal proliferations with alterations in plical architecture and a glandular component were classified as FTAs. Fallopian tube adenofibromas less than 3 mm were classified as incipient adenofibromas (iFTAs). The association of FTAs with ovarian adenofibromas (OAs) was also evaluated. Twenty-six of 28 (30% overall frequency) consecutively examined bilateral fallopian tube specimens contained adenofibromas (FTAs and iFTAs); all confined to the fimbria. Twelve FTAs were identified (11 cases; 14% frequency), 3 of which exceeded 1 cm. Twenty-nine iFTAs were identified (18 cases; 20% frequency); iFTAs were multiple in 10, bilateral in 4, and associated with an FTA in 3 cases. Three (25%) of 12 OAs with completely examined fallopian tubes were associated with FTAs. Stroma in both iFTAs and FTAs was CD10 and inhibin positive, and the epithelial phenotype of both iFTAs and OAs was identical, composed of secretory and ciliated cells. The fimbrial endosalpinx and the ovarian cortex share the potential for similar specialized stromal expansions with the formation of biphasic tumors with endosalpingeal epithelial differentiation. Similar to reports of serous and endometrioid tumors in both the distal fallopian tube and ovary, FTAs highlight a shared epithelial-mesenchymal differentiation pathway in the fimbrial-ovarian region. Whether the shared tumor phenotype in these 2 organs is coincidental or interdependent bears further investigation.