The purpose of the study is to develop a prognostic index model for the rare disease of mycosis fungoides and sezary syndrome. This will be done by collecting standardized clinical data at various institutions. The investigators hope this will enable the identification of low- and high-risk groups for survival in order to improve patient care and outcome.

Inclusion Criteria

• Diagnosis of advanced stage MF or SS (Stages IIB - IVB) within 6 months of presentation to the participating center
• Patients that are expected to have care administered at the participating center or jointly with referring physician(s) where follow-up data would be available

Exclusion Criteria

• Patients diagnosed with early stage MF/SS (Stages IA-IIA) before progressing to advanced stage
• Patients diagnosed with advanced MF/SS more than 6 months prior to initial presentation to the participating center
• Exclude one-time consultation type of new patients.

patients diagnosed with advanced stage mycosis fungoides and/or sezary syndrome