On immunohistochemical examination, the infiltrating cells were represented by two populations—CD3+/CD7+/CD5+ lymphocytes, with weak and uneven CD2 expression, negative for CD8, CD4, PAX5, TdT, CD68, CD14, CD56, and CD163, consistent with the diagnosis of peripheral T-cell lymphoma (Figure 3d), and MPO-positive cells (Figure 3c). The gene discussed is MPO; the disease is peripheral T-cell lymphoma, not otherwise specified.