Mycosis Fungoides

This schema is for Mycosis Fungoides (MF) and Sezary Disease (SD). The major difference between the two histologies is that for Sezary Disease, high amounts of cancerous T-cells are found in the blood. The distinction between the two histologies should be made by the pathologist or managing physician, not the registrar.

There are several phases for Mycosis Fungoides, patch (reddened, eczema-like rash), plaque/papules (small, raised bumps) and tumors on the skin (which may develop ulcers and become infected)

Lymph node involvement is based on clinically abnormal lymph nodes, and if confirmed pathologically, are further separated into clone negative, clone positive, and clone unknown

Metastatic disease includes visceral (non-cutaneous, extranodal) organ involvement, and carcinomatosis (clinically or pathologically confirmed)

There is one SSDI for Mycosis Fungoides and that is peripheral blood involvement. This is the “B” category that refers to the percentage of peripheral blood lymphocytes that are atypical. The percentage cutoffs are less than or equal to 5%, more than 5%, along with clone negative, clone positive, and clone unknown.

Treatment for Mycosis Fungoides and Sezary Disease includes photodynamic therapy, biological therapy, chemotherapy, targeted therapy, and checkpoint inhibitors

Updated: December 2, 2025