Paracortical axillary sentinel lymph node ectopic breast tissue

Abstract

Benign glandular inclusions in axillary lymph nodes are uncommon, and their presence in axillary sentinel lymph nodes is exceptionally rare. The possibility of over-staging due to misinterpretation of glandular inclusions as metastatic carcinoma is a concerning issue. We present a 54-year-old female with high grade ductal carcinoma in-situ undergoing simple mastectomy with sentinel lymph node biopsy. Permanent sections of the sentinel lymph node revealed scarce naked small glands without surrounding stroma scattered in the paracortex in the superficial level. Deeper levels showed glands spanning a much larger area (2 mm), with bland ducts and tubules separated by abundant stroma. The myoepithelial layer was visible and was immunohistochemically confirmed. A final diagnosis of benign ectopic breast tissue within an axillary sentinel lymph node was rendered. Previous studies described axillary sentinel lymph nodes with glandular inclusions separated by stroma or subcapsular in location. It has been suggested that paracortical location and absence of stroma are characteristics of metastasis. As demonstrated in our report, benign inclusions may be paracortical and lack surrounding stroma. We recommend that glandular inclusions should be a diagnostic consideration for cases in which paracortically located naked glands do not histologically resemble the corresponding primary tumor.