False-positive sentinel lymph nodes in breast cancer patients caused by benign glandular inclusions: report of three cases and review of the literature.

We report 3 cases of sentinel lymph nodes (SLNs) containing benign glandular inclusions (BGIs) in patients with breast carcinoma that were initially misdiagnosed as metastatic carcinoma. The first case had an SLN with glandular elements adjacent to a squamous inclusion cyst, the second had an SLN with a single complex gland showing apocrine features, and the third had 2 SLNs, each containing rare glands lined by bland columnar cells and surrounded by thin, fibrous bands. All glandular elements were distinctly different from the corresponding invasive carcinoma. Immunostains for myoepithelial markers revealed smooth muscle myosin reactivity and scattered p63+ nuclei, indicating the presence of myoepithelial cells. Based on morphologic and immunohistochemical findings, a diagnosis of BGIs was established. Our case series report indicates that comparison with the morphologic features of primary breast carcinoma and using immunohistochemical analysis for myoepithelial markers are important ancillary tools in distinguishing BGIs from metastatic carcinoma.