“…Lymphocyte-rich thymoma is a proliferation of numerous small lymphocytes with fewer epithelial cells.3 Cytologically, small reptilian lymphocytes range from 8 to 10 μm in diameter, which is within the range of the lymphocytes in this case (i.e., 7-9 μm). 4 As small lymphocytes can be present in both lymphocyte-rich thymoma and lymphoma, histology was required to screen for an epithelial component. An epithelial component to the neoplasm was ruled out using immunohistochemistry for pancytokeratin (intermediate filament of epithelial cells), consistent with lymphoma.…”