Cutaneous T cell lymphoma (CTCL) is a rare type of non-Hodgkin lymphoma that develops in the T cells. Mycosis fungoides (MF) and Sézary syndrome (SS) are two types of CTCL that mainly present in the skin. However, MF and SS can also be found in the lymph nodes, viscera, and blood. Consequently, the assessment of other white blood cells in the blood, namely CD4+/CD7-, or CD4+/CD26, is important to accurately stage these syndromes. This article reflects on the presentations that took place at the European Organisation for the Research and Treatment of Cancer (EORTC) Cutaneous Lymphoma Group 2021 Congress and discusses the role of blood involvement and treatment options in CTCL.