GTSF1 and primary cutaneous T-cell non-Hodgkin lymphoma: Subsequently, when we studied the DEGs enriched in both (1) early vs. mid and late CTCL and (2) stage I vs. stage IV disease, four genes were differentially expressed: TOX (involved in chromatin processes and T-cell development), FYB (T-cell adaptor protein), and GTSF1 (germ cell maintenance) were upregulated, and LTBP4 (latent TGF-beta binding protein) was downregulated in later CTCL stages.