Fine Needle Cytology and Flow Cytometry of Ectopic Cervical Thymoma: A Case Report

Background A case of ectopic cervical thymoma (ECT) in which fine needle cytology (FNC) and flow cytometry (FC) have orientated the cytologic diagnosis, is described. Case A 57-year-old woman underwent FNC of a right latero-cervical nodule. The smear showed a dispersed lymphoid-cell population; therefore, a second FNC was used for FC and to prepare a cell block. Smears were highly cellular. Cells were medium or large sized, with scanty cytoplasm and nuclei with dispersed chromatin ; large cells showed evident nucleoli. Immunohistochemistry on additional smears were positive for CD45RO and Ki67 in most of the cells, and negative for CK pan, CD20, thyreoglobulin and calcitonin. FC showed the following phenotype: CD2/CD3/CD7 = 67%, CD10 = 61 %, CD4/CD8 = 62%. CD19 and light chains were not expressed. A diagnosis of T-cell lymphoid proliferation was made and ECT was suggested; histological diagnosis was cervical ectopic benign type B1 thymoma. Conclusion FC may support the FNC diagnosis of ECT because of the specific phenotype of lymphoid cells showing the profile of "polyclonal" (CD2/CD3/CD7+) and thymic T-cells (CD10+, CD4/CD6+). FNC and FC may suggest the diagnosis of ECT even in the absence of detectable epithelial cells.