What is the pathophysiology of mycosis fungoides cutaneous T-cell lymphoma (CTCL)?

Updated: Apr 20, 2020
  • Author: Lauren C Pinter-Brown, MD; Chief Editor: Emmanuel C Besa, MD  more...
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Mycosis fungoides is a malignant lymphoma characterized by the expansion of a clone of CD4+ (or helper) memory T cells (CD45RO+) that normally patrol and home in on the skin. [6] The malignant clone frequently lacks normal T-cell antigens such as CD2, CD5, or CD7.

The normal and malignant cutaneous T cells home in on the skin through interactions with dermal capillary endothelial cells. Cutaneous T cells express cutaneous lymphocyte antigen (CLA), an adhesion molecule that mediates tethering of the T lymphocyte to endothelial cells in cutaneous postcapillary venules via its interaction with E selectin. [43]

Further promoting the proclivity of the cutaneous T cell to home in on the skin is the release by keratinocytes of cytokines, which infuse the dermis, coat the luminal surface of the dermal endothelial cells, and upregulate the adhesion molecules in the dermal capillary endothelial lumen, which react to CC chemokine receptor 4 (CCR4) found on cutaneous T cells.

Extravasating into the dermis, the cells show an affinity for the epidermis, clustering around Langerhans cells (as seen microscopically as Pautrier microabscesses). However, the malignant cells that adhere to the skin retain the ability to exit the skin via afferent lymphatics. They travel to lymph nodes and then through efferent lymphatics back to the blood to join the circulating population of CLA-positive T cells.

Thus, mycosis fungoides is fundamentally a systemic disease, even when the disease appears to be in an early stage and clinically limited to the skin.

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