Heterotopic tissue in lymph nodes is rare. Benign glandular lymph node inclusions (BGI) occur in 11.4% on average. Their histogenesis is still obscure. We studied 34 out of 1,039 cases of retroperitoneal lymph nodes with BGI (3.35%) of women who were treated by radical hysterectomy by Wertheim-Meigs of a cervical carcinoma. The nodes were reexamined by light microscopy and in 19 cases the antibodies MAK 6 (cytokeratine cocktail), HEA 125, Ber EP-4 (for differentiation between mesothelium and glandular differentiation), vimentin and CEA were additionally used. All BGI showed a strong expression of MAK 6 and in 57.9% and 73.7% to HEA 125 and Ber EP-4, respectively. Positive reaction against vimentin occured in 47.3%, but often only single cells were positive. None but one metastasis of an endometrioid adenocarcinoma of the cervix uteri of BGI expressed CEA. The BGI showed a capsular, trabecular or interfollicular location in more than 80% and in 44.1% an admixture of several cells at the lining epithelium was noted. No features usually associated with endometriosis, such as periglandular stroma or evidence of recent or old hemorrhage were seen. The results suggest that the BGI represent an endosalpingiosis and is therefore of secondary Müllerian origin. Some light microscopic features favoring the benign origin (location in the nodes, lining cells of multiple types, lack of mitoses and cellular atypism, no desmoplastic stroma reaction, presence of periglandular basement membrane) may be helpful in distinguishing metastasis of serous ovarian borderline tumors. Negative reaction against CEA and the cellular morphology can preclude metastases of an endometrioid adenocarcinoma of the cervix uteri as well as of a mucinous ovarian borderline tumor.