Difference between sentinel and non-sentinel lymph nodes in the distribution of dendritic cells and macrophages: An immunohistochemical and morphometric study using gastric regional nodes obtained in sentinel node navigation surgery for early gastric cancer.

The sentinel lymph node (SN) concept has a significant impact on cancer surgery. We aimed to examine which morphology of dendritic cells (DCs) and macrophages corresponds to "preconditioning" of the SN against cancer. Although macrophages are generally able to tolerate cancer metastasis, the CD169-positive subtype is believed to be a limited exception. Immunohistochemical and morphometric analyses were performed to examine DC-SIGN-, CD68-, and CD169-positive cells in SNs and non-SNs of 23 patients with gastric cancer with or without nodal metastasis. All patients survived for >5 years without recurrence. DCs were present in the subcapsular, paracortical, and medullary sinuses, the endothelia of which expressed DC-SIGN and smooth muscle actin (SMA). In the non-SNs of patients without metastasis, subcapsular DCs occupied a larger area than SNs, and this difference was statistically significant. Conversely, subcapsular DCs were likely to have migrated to the paracortical area of the SNs. DC clusters often overlapped with macrophage clusters; however, histiocytosis-like clusters of CD169-negative macrophages showed a smaller overlap. We found a significantly larger overlap between DC-SIGN and CD169-positive clusters in SNs than in non-SNs; the larger overlap seemed to correspond to a higher cross-presentation of cancer antigens between these cell populations. DC-SIGN-CD169-double positive cells might exist within this overlap. SNs in gastric cancers are usually preconditioned as a frontier of cancer immunity, but they may sometimes be suppressed earlier than non-SNs. DC-SIGN- and CD169-positive cells appeared to decrease owing to a long lag time from the primary lesion occurrence and a short distance from the metastasis.