Langerhans cells proliferation in ectopic micronodular thymoma with lymphoid stroma: a case report.

Ectopic micronodular thymoma (MNT) is a rare tumor. We described a 76-year-old woman, who was referred to our institutional for a mass in the left cervical region. The Magnetic Resonance Imaging (MRI) scan showed a 3.7 cm × 1.7 cm × 2.0 cm mass. The neoplasm was composed of epithelial tumor cells arranged in a micronodular growth pattern set in a stroma showing lymphoid hyperplasia with germinal centers. Immunohistochemical studies showed that the neoplastic epithelial cells were reactive for AE1/AE3, CK5/6, P63, and the lymphoid component to be of mixed B- and immature T-cell lineage. Langerhans cells were confirmed within epithelial nodules for the first time with langerin, S-100, CD1a expression. We report a case of cervical ectopic MNT to emphasize the langerhans cells proliferation and the histopathologic features and differential diagnosis of the rare lesion to promote a better and broader understanding of this less understood subject.