Benign epithelial inclusions in axillary lymph nodes: report of 18 cases and review of the literature.

The occurrence of various types of heterotopic epithelial structures in lymph nodes is a well-documented phenomenon. Here, we report on the presence of such inclusions in axillary lymph nodes. A total of 18 cases were identified. All patients were women, their ages ranging from 32 to 79 years (median, 57 y). Thirteen patients had concomitant or antecedent breast abnormalities, and 12 of them had undergone nodal sampling for staging purposes. The other 5 patients had noted enlarging axillary masses, with no clinical evidence of previous or concomitant breast or genital tract pathology. We classified the nodal inclusions on morphologic grounds into 3 main categories: those composed exclusively of glandular structures (glandular-type inclusions; 10 cases, 56%); those made up only of squamous cysts (squamous-type inclusions; 2 cases, 11%); and those containing both glandular and squamous epithelia (mixed glandular-squamous-type inclusions; 6 cases, 33%). We speculate about the possible mechanism for the migration of the epithelial cells into the lymph nodes, discuss the modifications that they may later undergo as a result of local and systemic factors, and consider the differential diagnosis with other conditions, particularly with metastatic well-differentiated breast carcinoma.