Micronodular thymic tumor with lymphoid stroma: A case report and review of the literature

Figure 2 Immunohistochemical photographs of tumor tissue (×20). A: Immunohistochemical staining for CD5. CD5 was expressed in the tumor epithelium, and the expression of CD5 in epithelial cells was diffuse and bright. The positive expression of CD5 was also observed in peripheral T lymphocytes; B: Immunohistochemical staining for CD20. CD20 was not expressed in the tumor epithelium, but it was positive in B lymphocytes in the stroma. CD20 expression was negative in tumor cells; C: Immunohistochemical staining for TdT. TdT (+) immature T cells were not found in tumor tissue, indicating that there were no immature lymphocytes in the thymoma; D: Immunohistochemical staining for Ki-67. The positive expression rate of Ki-67 reached up to 30% in the tumor cells. The germinal center lymphocytes in the background showed high expression of Ki-67.